sort_utils.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
#include <gtest/gtest.h>
 
#include <algorithm>
#include <chrono>
#include <cstdint>
#include <cstdlib>
#include <limits>
#include <random>
#include <string>
#include <type_traits>
#include <vector>
#include <array>
 
#include <tpl_sort_utils.H>
#include <tpl_dynArray.H>
#include <tpl_array.H>
#include <tpl_dynList.H>
#include <tpl_dynDlist.H>
#include <tpl_dnode.H>
 
using namespace Aleph;
using namespace std;
 
namespace {
 
static_assert(CountingSortable<int>);
static_assert(CountingSortable<unsigned long long>);
static_assert(not CountingSortable<bool>);
static_assert(RadixSortable<int>);
static_assert(RadixSortable<unsigned long long>);
static_assert(not RadixSortable<bool>);
 
static DynArray<int> make_dynarray(std::initializer_list<int> xs)
{
  DynArray<int> a;
  a.reserve(xs.size());
  size_t i = 0;
  for (const int x : xs)
    a(i++) = x;
  return a;
}
 
static DynList<int> make_dynlist(std::initializer_list<int> xs)
{
  DynList<int> l;
  for (int x : xs)
    l.append(x);
  return l;
}
 
static DynDlist<int> make_dyndlist(std::initializer_list<int> xs)
{
  DynDlist<int> l;
  for (int x : xs)
    l.append(x);
  return l;
}
 
static Dnode<int> make_dnode_list(std::initializer_list<int> xs)
{
  Dnode<int> h;
  for (int x : xs)
    h.append(new Dnode<int>(x));
  return h;
}
 
static void delete_all_nodes(Dnode<int> & h)
{
  while (not h.is_empty())
    delete h.remove_first_ne();
}
 
template <typename T>
static void sort_dynarray(DynArray<T> & a)
{
  quicksort(a);
}
 
template <typename T>
static void expect_same_dynarray(const DynArray<T> & a, const DynArray<T> & b)
{
  EXPECT_EQ(a.size(), b.size());
  if (a.size() != b.size())
    return;
  for (size_t i = 0; i < a.size(); ++i)
    EXPECT_EQ(a(i), b(i));
}
 
template <typename T>
static DynArray<uintptr_t> dynlist_node_addresses(const DynList<T> & l)
{
  DynArray<uintptr_t> ret;
  ret.reserve(l.size());
  size_t i = 0;
  for (HTList::Iterator it(l); it.has_curr(); it.next())
    ret(i++) = reinterpret_cast<uintptr_t>(it.get_curr());
  sort_dynarray(ret);
  return ret;
}
 
template <typename T>
static DynArray<uintptr_t> dyndlist_node_addresses(const DynDlist<T> & l)
{
  DynArray<uintptr_t> ret;
  ret.reserve(l.size());
  size_t i = 0;
  for (typename Dnode<T>::Iterator it(l); it.has_curr(); it.next())
    ret(i++) = reinterpret_cast<uintptr_t>(it.get_curr());
  sort_dynarray(ret);
  return ret;
}
 
TEST(SortUtilsSortedness, allows_equal)
{
  DynList<int> l = make_dynlist({1, 1, 2, 2, 3});
  EXPECT_TRUE(is_sorted(l));
  EXPECT_TRUE(test_sorted(l).first);
  EXPECT_TRUE(search_inversion(l).first);
}
 
TEST(SortUtilsSortedness, detects_inversion)
{
  DynList<int> l = make_dynlist({1, 3, 2, 4});
  EXPECT_FALSE(is_sorted(l));
  auto inv = search_inversion(l);
  EXPECT_FALSE(inv.first);
  EXPECT_EQ(inv.second, 2u);
}
 
TEST(SortUtilsSortedness, inversely_sorted)
{
  DynList<int> l = make_dynlist({5, 4, 4, 2, 1});
  EXPECT_TRUE(is_inversely_sorted(l));
  EXPECT_FALSE(is_sorted(l));
}
 
TEST(SortUtilsArraySorts, selection_sort_empty_and_single)
{
  int a0[1] = {0};
  selection_sort(a0, 0);
  selection_sort(a0, 1);
  EXPECT_EQ(a0[0], 0);
}
 
TEST(SortUtilsArraySorts, selection_sort_basic)
{
  int a[] = {3, 1, 2, 1, 0};
  selection_sort(a, sizeof(a) / sizeof(a[0]));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, insertion_sort_subrange)
{
  auto a = make_dynarray({10, 9, 3, 2, 1, 8, 7});
  // sort only [2..4] (3,2,1)
  insertion_sort(a, 2, 4);
  EXPECT_EQ(a(0), 10);
  EXPECT_EQ(a(1), 9);
  EXPECT_EQ(a(2), 1);
  EXPECT_EQ(a(3), 2);
  EXPECT_EQ(a(4), 3);
  EXPECT_EQ(a(5), 8);
  EXPECT_EQ(a(6), 7);
}
 
TEST(SortUtilsArraySorts, selection_sort_dynarray)
{
  auto a = make_dynarray({3, 1, 2, 1, 0});
  selection_sort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, selection_sort_dynarray_custom_compare_desc)
{
  auto a = make_dynarray({3, 1, 2, 1, 0});
  selection_sort(a, Aleph::greater<int>());
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_GE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, bubble_sort_dynarray)
{
  auto a = make_dynarray({3, 1, 2, 1, 0});
  bubble_sort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, bubble_sort_dynarray_already_sorted_with_duplicates)
{
  auto a = make_dynarray({0, 0, 1, 1, 2, 2});
  bubble_sort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
  EXPECT_EQ(a(0), 0);
  EXPECT_EQ(a(5), 2);
}
 
static bool is_min_heap(const DynArray<int> & a, size_t n)
{
  if (n <= 1)
    return true;
 
  for (size_t child = 2; child <= n; ++child)
    {
      size_t parent = child / 2;
      if (a(parent - 1) > a(child - 1))
        return false;
    }
  return true;
}
 
TEST(SortUtilsHelpers, select_pivot_op_dynarray_median_of_three)
{
  auto a = make_dynarray({5, 99, 0, 99, 99, 3, 99});
  // l=0 => 5, m=3 => 99, r=6 => 99 => median is 99 => either m or r
  long p = select_pivot_op<int>(a, 0, 6);
  EXPECT_TRUE(p == 3 || p == 6);
 
  auto b = make_dynarray({10, 99, 5, 99, 99, 99, 0});
  // l=0 => 10, m=3 => 99, r=6 => 0 => median is 10 => l
  EXPECT_EQ(select_pivot_op<int>(b, 0, 6), 0);
 
  auto c = make_dynarray({0, 99, 99, 5, 99, 99, 10});
  // l=0 => 0, m=3 => 5, r=6 => 10 => median is 5 => m
  EXPECT_EQ(select_pivot_op<int>(c, 0, 6), 3);
}
 
TEST(SortUtilsHelpers, select_pivot_op_array_small_range_returns_r)
{
  Array<int> a;
  for (int x : {5, 4, 3, 2, 1, 0})
    a.append(x);
 
  // r - l <= 5 => returns r
  EXPECT_EQ(select_pivot_op<int>(a, 0, 5), 5);
}
 
TEST(SortUtilsHelpers, partition_op_dynarray_invariants)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  std::vector<int> before;
  before.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    before.push_back(a(i));
 
  long p = partition_op<int>(a, 0, static_cast<long>(a.size() - 1));
  ASSERT_GE(p, 0);
  ASSERT_LT(static_cast<size_t>(p), a.size());
 
  const int pivot = a(p);
  for (long i = 0; i < p; ++i)
    ASSERT_FALSE(Aleph::less<int>()(pivot, a(i)));
  for (long i = p + 1; i < static_cast<long>(a.size()); ++i)
    ASSERT_FALSE(Aleph::less<int>()(a(i), pivot));
 
  std::vector<int> after;
  after.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    after.push_back(a(i));
  std::sort(before.begin(), before.end());
  std::sort(after.begin(), after.end());
  EXPECT_EQ(before, after);
}
 
TEST(SortUtilsHelpers, partition_op_array_invariants)
{
  Array<int> a;
  for (int x : {4, 1, 3, 2, 0, 2})
    a.append(x);
 
  std::vector<int> before;
  before.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    before.push_back(a(i));
 
  long p = partition_op<int>(a, 0, static_cast<long>(a.size() - 1));
  ASSERT_GE(p, 0);
  ASSERT_LT(static_cast<size_t>(p), a.size());
 
  const int pivot = a(p);
  for (long i = 0; i < p; ++i)
    ASSERT_FALSE(Aleph::less<int>()(pivot, a(i)));
  for (long i = p + 1; i < static_cast<long>(a.size()); ++i)
    ASSERT_FALSE(Aleph::less<int>()(a(i), pivot));
 
  std::vector<int> after;
  after.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    after.push_back(a(i));
  std::sort(before.begin(), before.end());
  std::sort(after.begin(), after.end());
  EXPECT_EQ(before, after);
}
 
TEST(SortUtilsHelpers, __random_select_dynarray_and_array)
{
  {
    auto a = make_dynarray({4, 1, 3, 2, 0, 2});
    auto expected = std::vector<int>{4, 1, 3, 2, 0, 2};
    std::sort(expected.begin(), expected.end());
    EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 0, 0, 5)), expected[0]);
    EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 3, 0, 5)), expected[3]);
    EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 5, 0, 5)), expected[5]);
  }
 
  {
    Array<int> a;
    for (int x : {4, 1, 3, 2, 0, 2})
      a.append(x);
    auto expected = std::vector<int>{4, 1, 3, 2, 0, 2};
    std::sort(expected.begin(), expected.end());
    EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 0, 0, 5)), expected[0]);
    EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 3, 0, 5)), expected[3]);
    EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 5, 0, 5)), expected[5]);
  }
}
 
TEST(SortUtilsHelpers, back_index_and_negate_compare)
{
  EXPECT_EQ(back_index(10), 9);
 
  auto nc = Negate_Compare<int, Aleph::less<int>>(Aleph::less<int>());
  EXPECT_TRUE(nc(2, 1));
  EXPECT_FALSE(nc(1, 2));
}
 
TEST(SortUtilsHelpers, select_pivot_and_partition_raw)
{
  int a[] = {4, 1, 3, 2, 0, 2};
  Aleph::less<int> cmp;
  int p = select_pivot<int, Aleph::less<int>>(a, 0, 5, cmp);
  EXPECT_GE(p, 0);
  EXPECT_LE(p, 5);
 
  int q = partition<int, Aleph::less<int>>(a, 0, 5, cmp);
  EXPECT_GE(q, 0);
  EXPECT_LE(q, 5);
}
 
TEST(SortUtilsHelpers, merge_raw_partitions)
{
  // [0..2] and [3..5] are already sorted
  int a[] = {0, 2, 4, 1, 3, 5};
  merge(a, 0, 2, 5, Aleph::less<int>());
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsHelpers, push2_fixedstack)
{
  FixedStack<int> st(10);
  push2(st, 1, 2);
  EXPECT_EQ(st.pop(), 1);
  EXPECT_EQ(st.pop(), 2);
  EXPECT_TRUE(st.is_empty());
}
 
TEST(SortUtilsHelpers, quicksort_no_tail_pointer)
{
  int a[] = {5, 4, 3, 2, 1, 0, 0, 9};
  quicksort_no_tail(a, 0, static_cast<int>((sizeof(a) / sizeof(a[0])) - 1));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsHelpers, compare_tnode_direct)
{
  Snodenc<int> n1(1), n2(2);
  auto cmp = Compare_Tnode<Slinknc, Snodenc, int, Aleph::less<int>>(Aleph::less<int>());
  EXPECT_TRUE(cmp(static_cast<Slinknc *>(&n1), static_cast<Slinknc *>(&n2)));
  EXPECT_TRUE(cmp(static_cast<Slinknc *>(&n1), 5));
}
 
TEST(SortUtilsHelpers, insert_sorted_dlink_and_list_insertion_sort)
{
  Dnode<int> h;
  Dlink & base = static_cast<Dlink &>(h);
 
  auto * n2 = new Dnode<int>(2);
  auto * n0 = new Dnode<int>(0);
  auto * n1 = new Dnode<int>(1);
 
  using Cmp = Compare_Dnode<int, Aleph::less<int>>;
  Cmp cmp{Aleph::less<int>()};
 
  insert_sorted<Cmp>(base, n2, cmp);
  insert_sorted<Cmp>(base, n0, cmp);
  insert_sorted<Cmp>(base, n1, cmp);
  EXPECT_EQ(search_extreme<int>(h, Aleph::less<int>())->get_data(), 0);
 
  // list_insertion_sort on Dlink
  Dnode<int> h2 = make_dnode_list({3, 1, 2, 0});
  Dlink & base2 = static_cast<Dlink &>(h2);
  list_insertion_sort<Dlink, Cmp>(base2, cmp);
  EXPECT_EQ(search_extreme<int>(h2, Aleph::less<int>())->get_data(), 0);
 
  delete_all_nodes(h);
  delete_all_nodes(h2);
}
 
TEST(SortUtilsHelpers, insert_sorted_htlist_and_list_insertion_sort)
{
  DynList<int> l;
  l.append(0);
  l.append(2);
 
  auto * node = new Snodenc<int>(1);
  Compare_Snodenc<int, Aleph::less<int>> cmp{Aleph::less<int>()};
  insert_sorted(l, static_cast<Slinknc *>(node), cmp);
  EXPECT_TRUE(is_sorted(l));
 
  DynList<int> l2;
  for (int x : {3, 1, 2, 0})
    l2.append(x);
  list_insertion_sort<HTList, Compare_Snodenc<int, Aleph::less<int>>>(
    static_cast<HTList &>(l2), cmp);
  EXPECT_TRUE(is_sorted(l2));
}
 
TEST(SortUtilsHelpers, dlink_random_search_and_dlink_random_select)
{
  auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
  Dlink & base = static_cast<Dlink &>(h);
 
  using Cmp = Compare_Dnode<int, Aleph::less<int>>;
  Cmp cmp{Aleph::less<int>()};
 
  auto * found = dlink_random_search(base, 3, cmp);
  ASSERT_NE(found, nullptr);
  EXPECT_EQ(found->get_data(), 3);
 
  auto * sel = dlink_random_select(base, 0, cmp);
  ASSERT_NE(sel, nullptr);
  EXPECT_EQ(static_cast<Dnode<int> *>(sel)->get_data(), 0);
 
  delete_all_nodes(h);
}
 
TEST(SortUtilsHelpers, binindex_explicit)
{
  const auto a = make_dynarray({0, 1, 1, 1, 2, 3});
  EXPECT_EQ(binindex(a, 2), 4);
}
 
TEST(SortUtilsHelpers, __random_select_raw_pointer)
{
  int a[] = {4, 1, 3, 2, 0, 2};
  std::vector<int> expected(std::begin(a), std::end(a));
  std::sort(expected.begin(), expected.end());
 
  Aleph::less<int> cmp;
  EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 0, 0, 5, cmp)), expected[0]);
  EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 3, 0, 5, cmp)), expected[3]);
  EXPECT_EQ((Aleph::__random_select<int, Aleph::less<int>>(a, 5, 0, 5, cmp)), expected[5]);
}
 
TEST(SortUtilsHelpers, sift_up_and_sift_down_restore_min_heap)
{
  Aleph::less<int> cmp;
 
  // sift_up: insert new element at end and bubble up
  {
    DynArray<int> a;
    a.reserve(4);
    a(0) = 1;
    a(1) = 3;
    a(2) = 5;
    a(3) = 0;
    sift_up<int, Aleph::less<int>>(a, 4, cmp);
    EXPECT_TRUE(is_min_heap(a, 4));
  }
 
  // sift_down: restore heap after root replaced
  {
    DynArray<int> a;
    a.reserve(4);
    a(0) = 3;
    a(1) = 1;
    a(2) = 2;
    a(3) = 0; // outside heap when n=3
    sift_down<int, Aleph::less<int>>(a, 3, cmp);
    EXPECT_TRUE(is_min_heap(a, 3));
  }
}
 
TEST(SortUtilsArraySorts, mergesort_pointer)
{
  int a[] = {5, 4, 3, 2, 1, 0, 0, 9};
  mergesort(a, 0, static_cast<int>((sizeof(a) / sizeof(a[0])) - 1));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, quicksort_pointer)
{
  int a[] = {5, 4, 3, 2, 1, 0, 0, 9};
  quicksort(a, 0, static_cast<int>((sizeof(a) / sizeof(a[0])) - 1));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, quicksort_rec_pointer)
{
  int a[] = {5, 4, 3, 2, 1, 0, 0, 9};
  quicksort_rec(a, 0, static_cast<int>((sizeof(a) / sizeof(a[0])) - 1));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, quicksort_rec_min_pointer)
{
  int a[] = {5, 4, 3, 2, 1, 0, 0, 9};
  quicksort_rec_min(a, 0, static_cast<int>((sizeof(a) / sizeof(a[0])) - 1));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, quicksort_insertion_pointer)
{
  int a[] = {9, 1, 8, 2, 7, 3, 6, 4, 5, 0};
  quicksort_insertion(a, 0, static_cast<int>((sizeof(a) / sizeof(a[0])) - 1));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
 
  int b[] = {2, 1};
  quicksort_insertion(b, 0, 1);
  EXPECT_TRUE(std::is_sorted(std::begin(b), std::end(b)));
}
 
// Introsort tests - hybrid algorithm with O(n log n) guaranteed
TEST(SortUtilsArraySorts, introsort_pointer_basic)
{
  int a[] = {5, 4, 3, 2, 1, 0, 0, 9};
  introsort(a, 0L, static_cast<long>((sizeof(a) / sizeof(a[0])) - 1));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, introsort_pointer_convenience)
{
  int a[] = {9, 1, 8, 2, 7, 3, 6, 4, 5, 0};
  introsort(a, sizeof(a) / sizeof(a[0]));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, introsort_pointer_custom_compare)
{
  int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
  introsort(a, 0L, 8L, std::greater<int>());
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a), std::greater<int>()));
}
 
TEST(SortUtilsArraySorts, introsort_dynarray)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  introsort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, introsort_empty_and_single)
{
  // Empty array
  int empty[] = {0};
  introsort(empty, 0);
  EXPECT_EQ(empty[0], 0);
 
  // Single element
  int single[] = {42};
  introsort(single, 1);
  EXPECT_EQ(single[0], 42);
 
  // Empty DynArray
  DynArray<int> da;
  EXPECT_NO_THROW(introsort(da));
}
 
TEST(SortUtilsArraySorts, introsort_already_sorted)
{
  int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
  introsort(a, sizeof(a) / sizeof(a[0]));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, introsort_reverse_sorted)
{
  int a[] = {10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
  introsort(a, sizeof(a) / sizeof(a[0]));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, introsort_all_equal)
{
  int a[] = {5, 5, 5, 5, 5, 5, 5, 5, 5, 5};
  introsort(a, sizeof(a) / sizeof(a[0]));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, introsort_large_array_forces_heapsort)
{
  // Create an array large enough that might trigger heapsort fallback
  // This tests the depth limit mechanism
  const size_t n = 10000;
  std::vector<int> v(n);
  for (size_t i = 0; i < n; ++i)
    v[i] = static_cast<int>(n - i); // Reverse sorted (worst case for quicksort)
 
  introsort(v.data(), n);
  EXPECT_TRUE(std::is_sorted(v.begin(), v.end()));
}
 
TEST(SortUtilsArraySorts, introsort_dynarray_large)
{
  // Test with larger DynArray
  const size_t n = 5000;
  DynArray<int> a;
  a.reserve(n);
  for (size_t i = 0; i < n; ++i)
    a(i) = static_cast<int>(n - i); // Reverse sorted
 
  introsort(a);
  for (size_t i = 1; i < n; ++i)
    ASSERT_LE(a(i - 1), a(i)) << "Failed at index " << i;
}
 
// Introsort with STL-style pointer interface (begin, end)
TEST(SortUtilsArraySorts, introsort_pointer_begin_end)
{
  int a[] = {9, 1, 8, 2, 7, 3, 6, 4, 5, 0};
  introsort(a, a + 10);  // STL-style: introsort(begin, end)
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsArraySorts, introsort_pointer_begin_end_partial)
{
  int a[] = {9, 1, 8, 2, 7, 3, 6, 4, 5, 0};
  // Sort only middle portion [2, 7)
  introsort(a + 2, a + 7);
  // Elements 0,1 unchanged, 2-6 sorted, 7-9 unchanged
  EXPECT_EQ(a[0], 9);
  EXPECT_EQ(a[1], 1);
  EXPECT_TRUE(std::is_sorted(a + 2, a + 7));
  EXPECT_EQ(a[7], 4);
}
 
TEST(SortUtilsArraySorts, introsort_pointer_begin_end_custom_compare)
{
  int a[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
  introsort(a, a + 9, std::greater<int>());
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a), std::greater<int>()));
}
 
TEST(SortUtilsArraySorts, introsort_pointer_begin_end_empty)
{
  int a[] = {42};
  // Empty range - should not crash
  introsort(a, a);
  EXPECT_EQ(a[0], 42);  // Unchanged
}
 
// Introsort for Array<T> container
TEST(SortUtilsArraySorts, introsort_array_container)
{
  Array<int> arr;
  arr.append(5);
  arr.append(2);
  arr.append(8);
  arr.append(1);
  arr.append(9);
  arr.append(3);
 
  introsort(arr);
 
  for (size_t i = 1; i < arr.size(); ++i)
    ASSERT_LE(arr(i - 1), arr(i));
}
 
TEST(SortUtilsArraySorts, introsort_array_container_custom_compare)
{
  Array<int> arr;
  for (int i = 1; i <= 10; ++i)
    arr.append(i);
 
  introsort(arr, std::greater<int>());
 
  for (size_t i = 1; i < arr.size(); ++i)
    ASSERT_GE(arr(i - 1), arr(i));  // Descending order
}
 
TEST(SortUtilsArraySorts, introsort_array_container_empty)
{
  Array<int> arr;
  EXPECT_NO_THROW(introsort(arr));
  EXPECT_TRUE(arr.is_empty());
}
 
TEST(SortUtilsArraySorts, introsort_array_container_single)
{
  Array<int> arr;
  arr.append(42);
  introsort(arr);
  EXPECT_EQ(arr.size(), 1u);
  EXPECT_EQ(arr(0), 42);
}
 
TEST(SortUtilsArraySorts, introsort_array_container_large)
{
  const size_t n = 5000;
  Array<int> arr(n);
  for (size_t i = 0; i < n; ++i)
    arr.append(static_cast<int>(n - i));  // Reverse sorted
 
  introsort(arr);
 
  for (size_t i = 1; i < n; ++i)
    ASSERT_LE(arr(i - 1), arr(i)) << "Failed at index " << i;
}
 
TEST(SortUtilsArraySorts, heapsort_dynarray)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  heapsort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, quicksort_op_dynarray)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  quicksort_op(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, quicksort_op_empty)
{
  DynArray<int> a;
  EXPECT_NO_THROW(quicksort_op(a));
  EXPECT_TRUE(a.is_empty());
}
 
TEST(SortUtilsArraySorts, shellsort_dynarray)
{
  auto a = make_dynarray({9, 1, 8, 2, 7, 3, 6, 4, 5, 0});
  shellsort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, quicksort_dynarray)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  quicksort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsArraySorts, quicksort_rec_dynarray)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  quicksort_rec(a, 0, static_cast<long>(a.size() - 1));
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsListSorts, mergesort_dynlist)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  mergesort(l);
  EXPECT_TRUE(is_sorted(l));
}
 
TEST(SortUtilsListSorts, mergeinsertsort_dynlist)
{
  DynList<int> l = make_dynlist({9, 8, 7, 6, 5, 4, 3, 2, 1, 0});
  mergeinsertsort(l, Aleph::less<int>(), 3);
  EXPECT_TRUE(is_sorted(l));
}
 
TEST(SortUtilsListSorts, insertion_sort_dynlist_rvalue)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  DynList<int> sorted = insertion_sort(std::move(l));
  EXPECT_TRUE(is_sorted(sorted));
  EXPECT_TRUE(l.is_empty());
}
 
TEST(SortUtilsListSorts, mergesort_dynlist_rvalue)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  DynList<int> sorted = mergesort(std::move(l));
  EXPECT_TRUE(is_sorted(sorted));
  EXPECT_TRUE(l.is_empty());
}
 
TEST(SortUtilsListSorts, quicksort_dynlist)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  quicksort(l);
  EXPECT_TRUE(is_sorted(l));
  EXPECT_EQ(l.get_first(), 0);
  EXPECT_EQ(l.get_last(), 4);
}
 
TEST(SortUtilsListSorts, merge_lists_dynlist)
{
  DynList<int> l1 = make_dynlist({0, 2, 4});
  DynList<int> l2 = make_dynlist({1, 3, 5});
  DynList<int> out;
 
  merge_lists(l1, l2, out, Aleph::less<int>());
  EXPECT_TRUE(l1.is_empty());
  EXPECT_TRUE(l2.is_empty());
  EXPECT_TRUE(is_sorted(out));
  EXPECT_EQ(out.size(), 6u);
  EXPECT_EQ(out.get_first(), 0);
  EXPECT_EQ(out.get_last(), 5);
}
 
TEST(SortUtilsListSorts, merge_lists_dnode)
{
  auto l1 = make_dnode_list({0, 2, 4});
  auto l2 = make_dnode_list({1, 3, 5});
  Dnode<int> out;
 
  merge_lists(l1, l2, out, Aleph::less<int>());
 
  EXPECT_TRUE(l1.is_empty());
  EXPECT_TRUE(l2.is_empty());
  EXPECT_FALSE(out.is_empty());
 
  int expected = 0;
  for (Dnode<int>::Iterator it(out); it.has_curr(); it.next_ne(), ++expected)
    EXPECT_EQ(it.get_curr_ne()->get_data(), expected);
  EXPECT_EQ(expected, 6);
 
  delete_all_nodes(out);
}
 
TEST(SortUtilsDyndlistSorts, mergesort_dyndlist)
{
  DynDlist<int> l = make_dyndlist({4, 1, 3, 2, 0, 2});
  mergesort(l);
  EXPECT_TRUE(is_sorted(l));
}
 
TEST(SortUtilsDyndlistSorts, search_extreme_min)
{
  DynDlist<int> l = make_dyndlist({4, 1, 3, 2, 0, 2});
  int * p = search_extreme(l);
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 0);
}
 
TEST(SortUtilsDyndlistSorts, random_select_dyndlist)
{
  DynDlist<int> l = make_dyndlist({4, 1, 3, 2, 0, 2});
  int * p = random_select(l, 0);
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 0);
 
  p = random_select(l, 5);
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 4);
}
 
TEST(SortUtilsDyndlistSorts, random_search_dyndlist)
{
  DynDlist<int> l = make_dyndlist({4, 1, 3, 2, 0, 2});
 
  int * p = random_search(l, 3);
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 3);
 
  p = random_search(l, 99);
  EXPECT_EQ(p, nullptr);
}
 
TEST(SortUtilsDnodeDlinkAlgorithms, random_select_and_random_search_on_dlink)
{
  auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
 
  auto * n0 = random_select<int>(h, 0);
  ASSERT_NE(n0, nullptr);
  EXPECT_EQ(n0->get_data(), 0);
 
  auto * nmax = random_select<int>(h, 5);
  ASSERT_NE(nmax, nullptr);
  EXPECT_EQ(nmax->get_data(), 4);
 
  auto * nfound = random_search<int>(h, 3);
  ASSERT_NE(nfound, nullptr);
  EXPECT_EQ(nfound->get_data(), 3);
 
  auto * nmiss = random_search<int>(h, 99);
  EXPECT_EQ(nmiss, nullptr);
 
  delete_all_nodes(h);
}
 
TEST(SortUtilsHTListPath, quicksort_htlist_via_dynlist)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  quicksort<int>(static_cast<HTList &>(l), Aleph::less<int>());
  EXPECT_TRUE(is_sorted(l));
}
 
TEST(SortUtilsSearchSequential, sequential_search_raw_array)
{
  int a[] = {4, 1, 3, 2, 0, 2};
  EXPECT_EQ(sequential_search(a, int{3}, 0, 5), 2);
  EXPECT_EQ(sequential_search(a, int{99}, 0, 5), Not_Found);
}
 
TEST(SortUtilsSearchSequential, sequential_search_dynarray)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  EXPECT_EQ(sequential_search(a, 3, 0, static_cast<int>(a.size() - 1)), 2);
  EXPECT_EQ(sequential_search(a, 99, 0, static_cast<int>(a.size() - 1)), Not_Found);
}
 
TEST(SortUtilsSearchSequential, sequential_search_dynlist)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  int * p = sequential_search(l, 3);
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 3);
 
  p = sequential_search(l, 99);
  EXPECT_EQ(p, nullptr);
}
 
TEST(SortUtilsSearchSequential, sequential_search_dyndlist)
{
  DynDlist<int> l = make_dyndlist({4, 1, 3, 2, 0, 2});
  int * p = sequential_search(l, 3);
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 3);
  p = sequential_search(l, 99);
  EXPECT_EQ(p, nullptr);
}
 
TEST(SortUtilsSearchSequential, sequential_search_dnode)
{
  auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
 
  auto * n = sequential_search(h, 3);
  ASSERT_NE(n, nullptr);
  EXPECT_EQ(n->get_data(), 3);
 
  n = sequential_search(h, 99);
  EXPECT_EQ(n, nullptr);
 
  delete_all_nodes(h);
}
 
TEST(SortUtilsSearchExtreme, search_extreme_dnode_min)
{
  auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
  auto * n = search_extreme<int>(h, Aleph::less<int>());
  ASSERT_NE(n, nullptr);
  EXPECT_EQ(n->get_data(), 0);
  delete_all_nodes(h);
}
 
TEST(SortUtilsSearchExtreme, search_min_max_raw_array)
{
  int a[] = {4, 1, 3, 2, 0, 2};
  EXPECT_EQ(search_min(a, 0, 5), 4);
  EXPECT_EQ(search_max(a, 0, 5), 0);
}
 
TEST(SortUtilsSearchExtreme, search_extreme_and_search_max_dynarray)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  EXPECT_EQ(search_extreme(a, 0, static_cast<long>(a.size() - 1)), 4);
  EXPECT_EQ(search_max(a, 0, static_cast<long>(a.size() - 1)), 0);
}
 
TEST(SortUtilsSearchExtreme, search_min_max_dyndlist)
{
  DynDlist<int> l = make_dyndlist({4, 1, 3, 2, 0, 2});
  int * mn = search_min(l);
  int * mx = search_max(l);
  ASSERT_NE(mn, nullptr);
  ASSERT_NE(mx, nullptr);
  EXPECT_EQ(*mn, 0);
  EXPECT_EQ(*mx, 4);
}
 
TEST(SortUtilsSearchExtreme, search_extreme_dynlist_min_max)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  int * mn = search_extreme(l);
  int * mx = search_extreme(l, Aleph::greater<int>());
  ASSERT_NE(mn, nullptr);
  ASSERT_NE(mx, nullptr);
  EXPECT_EQ(*mn, 0);
  EXPECT_EQ(*mx, 4);
}
 
TEST(SortUtilsSearchExtreme, search_min_max_dynlist)
{
  DynList<int> l = make_dynlist({4, 1, 3, 2, 0, 2});
  int * mn = search_extreme(l, Aleph::less<int>());
  int * mx = search_extreme(l, Aleph::greater<int>());
  ASSERT_NE(mn, nullptr);
  ASSERT_NE(mx, nullptr);
  EXPECT_EQ(*mn, 0);
  EXPECT_EQ(*mx, 4);
}
 
TEST(SortUtilsDnodeSorts, selection_insertion_quick_merge)
{
  {
    auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
    selection_sort(h, Aleph::less<int>());
    EXPECT_EQ(search_extreme<int>(h, Aleph::less<int>())->get_data(), 0);
    delete_all_nodes(h);
  }
 
  {
    auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
    insertion_sort(h);
    EXPECT_EQ(search_extreme<int>(h, Aleph::less<int>())->get_data(), 0);
    delete_all_nodes(h);
  }
 
  {
    auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
    quicksort(h);
    EXPECT_EQ(search_extreme<int>(h, Aleph::less<int>())->get_data(), 0);
    delete_all_nodes(h);
  }
 
  {
    auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
    mergesort(h);
    EXPECT_EQ(search_extreme<int>(h, Aleph::less<int>())->get_data(), 0);
    delete_all_nodes(h);
  }
}
 
TEST(SortUtilsDlinkSorts, quicksort_dlink)
{
  auto h = make_dnode_list({4, 1, 3, 2, 0, 2});
  Dlink & base = static_cast<Dlink &>(h);
 
  using Cmp = Compare_Dnode<int, Aleph::less<int>>;
  quicksort(base, Cmp(Aleph::less<int>()));
 
  EXPECT_EQ(search_extreme<int>(h, Aleph::less<int>())->get_data(), 0);
  EXPECT_EQ(search_extreme<int>(h, Aleph::greater<int>())->get_data(), 4);
 
  delete_all_nodes(h);
}
 
TEST(SortUtilsSearch, binary_search_dup_and_bsearch)
{
  auto a = make_dynarray({0, 1, 1, 1, 2, 3});
 
  auto idxs = binary_search_dup(a, 1);
  ASSERT_EQ(idxs.size(), 3u);
  EXPECT_EQ(idxs.get_first(), 1u);
  EXPECT_EQ(idxs.get_last(), 3u);
 
  int * p = bsearch(a, 1);
  ASSERT_NE(p, nullptr);
  EXPECT_EQ(*p, 1);
  EXPECT_EQ(bsearch(a, 99), nullptr);
}
 
TEST(SortUtilsSearch, binary_search_dup_boundary_cases)
{
  {
    auto a = make_dynarray({1, 1, 1, 2, 3});
    auto idxs = binary_search_dup(a, 1);
    ASSERT_EQ(idxs.size(), 3u);
    EXPECT_EQ(idxs.get_first(), 0u);
    EXPECT_EQ(idxs.get_last(), 2u);
  }
 
  {
    auto a = make_dynarray({0, 1, 2, 3, 3, 3});
    auto idxs = binary_search_dup(a, 3);
    ASSERT_EQ(idxs.size(), 3u);
    EXPECT_EQ(idxs.get_first(), 3u);
    EXPECT_EQ(idxs.get_last(), 5u);
  }
}
 
TEST(SortUtilsSearch, binary_search_dup_custom_compare_descending)
{
  // Descending sorted with duplicates
  auto a = make_dynarray({5, 4, 3, 3, 3, 2, 1, 1, 0});
  auto idxs = binary_search_dup(a, 3, Aleph::greater<int>());
  ASSERT_EQ(idxs.size(), 3u);
  EXPECT_EQ(idxs.get_first(), 2u);
  EXPECT_EQ(idxs.get_last(), 4u);
 
  idxs = binary_search_dup(a, 1, Aleph::greater<int>());
  ASSERT_EQ(idxs.size(), 2u);
  EXPECT_EQ(idxs.get_first(), 6u);
  EXPECT_EQ(idxs.get_last(), 7u);
}
 
TEST(SortUtilsSearch, bsearch_dup_custom_compare_descending)
{
  auto a = make_dynarray({5, 4, 3, 3, 3, 2, 1, 1, 0});
  auto ps = bsearch_dup(a, 3, Aleph::greater<int>());
  ASSERT_EQ(ps.size(), 3u);
  for (auto p : ps)
    {
      ASSERT_NE(p, nullptr);
      EXPECT_EQ(*p, 3);
    }
}
 
TEST(SortUtilsIndexBuild, build_index_and_build_index_ptr)
{
  auto a = make_dynarray({3, 1, 2, 1, 0});
 
  auto idx = build_index(a);
  ASSERT_EQ(idx.size(), a.size());
  for (size_t i = 1; i < idx.size(); ++i)
    ASSERT_LE(a(idx(i - 1)), a(idx(i)));
 
  auto ptrs = build_index_ptr(a);
  ASSERT_EQ(ptrs.size(), a.size());
  for (size_t i = 1; i < ptrs.size(); ++i)
    ASSERT_LE(*ptrs(i - 1), *ptrs(i));
}
 
TEST(SortUtilsSlinkncPath, sequential_search_and_search_extreme_on_slinknc)
{
  Slinknc head;
  auto * n1 = new Snodenc<int>(4);
  auto * n2 = new Snodenc<int>(1);
  auto * n3 = new Snodenc<int>(3);
  auto * n4 = new Snodenc<int>(0);
  head.insert(n1);
  head.insert(n2);
  head.insert(n3);
  head.insert(n4);
 
  auto found = sequential_search(head, 3);
  ASSERT_NE(found, nullptr);
  EXPECT_EQ(static_cast<Snodenc<int>*>(found)->get_data(), 3);
 
  auto missing = sequential_search(head, 99);
  EXPECT_EQ(missing, nullptr);
 
  auto extreme_min = search_extreme(head, Compare_Snodenc<int, Aleph::less<int>>(Aleph::less<int>()));
  ASSERT_NE(extreme_min, nullptr);
  EXPECT_EQ(static_cast<Snodenc<int>*>(extreme_min)->get_data(), 0);
 
  while (not head.is_empty())
    delete static_cast<Snodenc<int>*>(head.remove_next());
}
 
TEST(SortUtilsSlinkncPath, sequential_search_default_equal_on_slinknc)
{
  Slinknc head;
  auto * n1 = new Snodenc<int>(2);
  auto * n2 = new Snodenc<int>(1);
  auto * n3 = new Snodenc<int>(0);
  head.insert(n1);
  head.insert(n2);
  head.insert(n3);
 
  auto * found = sequential_search<int>(head, 1);
  ASSERT_NE(found, nullptr);
  EXPECT_EQ(found->to_data<int>(), 1);
 
  auto * missing = sequential_search<int>(head, 99);
  EXPECT_EQ(missing, nullptr);
 
  while (not head.is_empty())
    delete static_cast<Snodenc<int>*>(head.remove_next());
}
 
TEST(SortUtilsDlinkPath, sequential_search_and_selection_sort_on_dlink)
{
  auto h = make_dnode_list({3, 1, 2, 0});
  Dlink & base = static_cast<Dlink &>(h);
 
  auto * found = sequential_search<int>(base, 2);
  ASSERT_NE(found, nullptr);
  EXPECT_EQ(static_cast<Dnode<int>*>(found)->get_data(), 2);
 
  selection_sort(base, Compare_Dnode<int, Aleph::less<int>>(Aleph::less<int>()));
  auto * mn = search_extreme<int>(h, Aleph::less<int>());
  ASSERT_NE(mn, nullptr);
  EXPECT_EQ(mn->get_data(), 0);
 
  delete_all_nodes(h);
}
 
TEST(SortUtilsRandomSearch, random_search_raw_and_dynarray)
{
  int a[] = {4, 1, 3, 2, 0, 2};
  int idx = random_search(a, 3, 0, 5);
  ASSERT_NE(idx, Not_Found);
  EXPECT_EQ(a[idx], 3);
  EXPECT_EQ(random_search(a, 99, 0, 5), Not_Found);
 
  auto d = make_dynarray({4, 1, 3, 2, 0, 2});
  idx = random_search(d, 3, 0, static_cast<long>(d.size() - 1));
  ASSERT_NE(idx, Not_Found);
  EXPECT_EQ(d(idx), 3);
  EXPECT_EQ(random_search(d, 99, 0, static_cast<long>(d.size() - 1)), Not_Found);
}
 
TEST(SortUtilsRandomSelect, random_select_array_container)
{
  Array<int> a;
  for (int x : {4, 1, 3, 2, 0, 2})
    a.append(x);
 
  EXPECT_EQ(random_select(a, 0), 0);
  EXPECT_EQ(random_select(a, 5), 4);
}
 
TEST(SortUtilsRandomSelect, random_select_out_of_range_and_empty)
{
  {
    DynArray<int> a;
    EXPECT_THROW(random_select(a, 0), std::out_of_range);
  }
 
  {
    auto a = make_dynarray({4, 1, 3});
    EXPECT_THROW(random_select(a, 3), std::out_of_range);
  }
 
  {
    Array<int> a;
    a.append(1);
    EXPECT_THROW(random_select(a, 1), std::out_of_range);
  }
 
  {
    int b[] = {4, 1, 3};
    using Cmp = Aleph::less<int>;
    auto fn = static_cast<const int & (*)(int *, const long, const long, const Cmp &)>(
      &Aleph::random_select<int, Cmp>);
    EXPECT_THROW(fn(b, 3, 3, Cmp()), std::out_of_range);
  }
 
  {
    Dnode<int> h;
    EXPECT_EQ(random_select<int>(h, 0), nullptr);
    EXPECT_EQ(random_select<int>(h, 1), nullptr);
  }
 
  {
    DynDlist<int> l;
    EXPECT_EQ(random_select(l, 0), nullptr);
    EXPECT_EQ(random_select(l, 1), nullptr);
  }
 
  {
    auto h = make_dnode_list({4, 1});
    EXPECT_THROW(random_select<int>(h, 2), std::out_of_range);
    delete_all_nodes(h);
  }
 
  {
    auto l = make_dyndlist({4, 1});
    EXPECT_THROW(random_select(l, 2), std::out_of_range);
  }
}
 
TEST(SortUtilsSearch, binary_search_insertion_point_container)
{
  auto a = make_dynarray({0, 2, 4, 6});
 
  EXPECT_EQ(binary_search(a, 0), 0);
  EXPECT_EQ(binary_search(a, 6), 3);
 
  // insertion points
  EXPECT_EQ(binary_search(a, 1), 1);
  EXPECT_EQ(binary_search(a, 5), 3);
  EXPECT_EQ(binary_search(a, 7), 4);
}
 
TEST(SortUtilsSearch, binary_search_insertion_point_raw)
{
  int a[] = {0, 2, 4, 6};
  EXPECT_EQ(binary_search(a, 0, 0, 3), 0);
  EXPECT_EQ(binary_search(a, 6, 0, 3), 3);
  EXPECT_EQ(binary_search(a, 1, 0, 3), 1);
  EXPECT_EQ(binary_search(a, 5, 0, 3), 3);
  EXPECT_EQ(binary_search(a, 7, 0, 3), 4);
}
 
TEST(SortUtilsSearch, binary_search_rec_insertion_point_raw)
{
  int a[] = {0, 2, 4, 6};
  EXPECT_EQ(binary_search_rec(a, 0, 0, 3), 0);
  EXPECT_EQ(binary_search_rec(a, 6, 0, 3), 3);
  EXPECT_EQ(binary_search_rec(a, 1, 0, 3), 1);
  EXPECT_EQ(binary_search_rec(a, 5, 0, 3), 3);
  EXPECT_EQ(binary_search_rec(a, 7, 0, 3), 4);
}
 
TEST(SortUtilsSearch, random_select_dynarray_and_raw)
{
  auto a = make_dynarray({4, 1, 3, 2, 0, 2});
  EXPECT_EQ(random_select(a, 0), 0);
  EXPECT_EQ(random_select(a, 5), 4);
 
  int b[] = {4, 1, 3, 2, 0, 2};
  using Cmp = Aleph::less<int>;
  auto fn = static_cast<const int & (*)(int *, const long, const long, const Cmp &)>(
    &Aleph::random_select<int, Cmp>);
  EXPECT_EQ(fn(b, 0, 6, Cmp()), 0);
  EXPECT_EQ(fn(b, 5, 6, Cmp()), 4);
}
 
TEST(SortUtilsSearch, binary_search_ptr_container)
{
  auto a = make_dynarray({0, 2, 4, 6});
  DynArray<int *> idx;
  idx.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    idx(i) = &a(i);
 
  // already sorted pointers by value
  EXPECT_EQ(binary_search(idx, 0), 0);
  EXPECT_EQ(binary_search(idx, 6), 3);
  EXPECT_EQ(binary_search(idx, 1), 1);
  EXPECT_EQ(binary_search(idx, 7), 4);
}
 
TEST(SortUtilsSearch, bsearch_dup_and_binindex_dup)
{
  auto a = make_dynarray({0, 1, 1, 1, 2, 3});
  auto ptrs = bsearch_dup(a, 1);
  ASSERT_EQ(ptrs.size(), 3u);
  for (auto p : ptrs)
    ASSERT_NE(p, nullptr);
 
  auto idxs = binindex_dup(a, 1);
  ASSERT_EQ(idxs.size(), 3u);
  EXPECT_EQ(idxs.get_first(), 1);
  EXPECT_EQ(idxs.get_last(), 3);
}
 
TEST(SortUtilsSearch, bsearch_dup_ptr_container_custom_compare_descending)
{
  auto a = make_dynarray({5, 4, 3, 3, 3, 2, 1, 1, 0});
  DynArray<int *> ptrs;
  ptrs.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    ptrs(i) = &a(i);
 
  auto dup = bsearch_dup(ptrs, 3, Aleph::greater<int>());
  ASSERT_EQ(dup.size(), 3u);
  for (auto p : dup)
    {
      ASSERT_NE(p, nullptr);
      EXPECT_EQ(*p, 3);
    }
}
 
TEST(SortUtilsSearch, binindex_dup_ptr_container_custom_compare_descending)
{
  auto a = make_dynarray({5, 4, 3, 3, 3, 2, 1, 1, 0});
  DynArray<int *> ptrs;
  ptrs.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    ptrs(i) = &a(i);
 
  auto idxs = binindex_dup(ptrs, 3, Aleph::greater<int>());
  ASSERT_EQ(idxs.size(), 3u);
  EXPECT_EQ(idxs.get_first(), 2);
  EXPECT_EQ(idxs.get_last(), 4);
}
 
TEST(SortUtilsSearch, bsearch_dup_ptr_container)
{
  auto a = make_dynarray({0, 1, 1, 1, 2, 3});
  DynArray<int *> ptrs;
  ptrs.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    ptrs(i) = &a(i);
 
  auto found = bsearch(ptrs, 1);
  ASSERT_NE(found, nullptr);
  EXPECT_EQ(*found, 1);
 
  auto dup = bsearch_dup(ptrs, 1);
  ASSERT_EQ(dup.size(), 3u);
  for (auto p : dup)
    {
      ASSERT_NE(p, nullptr);
      EXPECT_EQ(*p, 1);
    }
}
 
TEST(SortUtilsSearch, binindex_dup_ptr_container)
{
  auto a = make_dynarray({0, 1, 1, 1, 2, 3});
  DynArray<int *> ptrs;
  ptrs.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    ptrs(i) = &a(i);
 
  auto idxs = binindex_dup(ptrs, 1);
  ASSERT_EQ(idxs.size(), 3u);
  EXPECT_EQ(idxs.get_first(), 1);
  EXPECT_EQ(idxs.get_last(), 3);
}
 
TEST(SortUtilsSearch, binary_search_ptr_container_custom_compare)
{
  auto a = make_dynarray({5, 4, 3, 2, 1, 0});
  DynArray<int *> ptrs;
  ptrs.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    ptrs(i) = &a(i);
 
  // The container is sorted in descending order, so we must use greater<int>
  EXPECT_EQ(binary_search(ptrs, 5, Aleph::greater<int>()), 0);
  EXPECT_EQ(binary_search(ptrs, 0, Aleph::greater<int>()), 5);
  EXPECT_EQ(binary_search(ptrs, 3, Aleph::greater<int>()), 2);
}
 
TEST(SortUtilsSearch, binary_search_ptr_container_range_less)
{
  auto a = make_dynarray({0, 1, 2, 3, 4, 5});
  DynArray<int *> ptrs;
  ptrs.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    ptrs(i) = &a(i);
 
  // search only in [2..4] => values {2,3,4}
  EXPECT_EQ(binary_search(ptrs, 3, 2, 4), 3);
 
  // insertion points within the restricted range
  EXPECT_EQ(binary_search(ptrs, 1, 2, 4), 2);
  EXPECT_EQ(binary_search(ptrs, 5, 2, 4), 5);
}
 
TEST(SortUtilsSearch, binary_search_ptr_container_range_greater)
{
  auto a = make_dynarray({5, 4, 3, 2, 1, 0});
  DynArray<int *> ptrs;
  ptrs.reserve(a.size());
  for (size_t i = 0; i < a.size(); ++i)
    ptrs(i) = &a(i);
 
  // search only in [1..3] => values {4,3,2} under greater<int>
  EXPECT_EQ(binary_search(ptrs, 3, 1, 3, Aleph::greater<int>()), 2);
 
  // insertion points within the restricted range for descending order
  // 5 would be inserted before 4 => at l
  EXPECT_EQ(binary_search(ptrs, 5, 1, 3, Aleph::greater<int>()), 1);
  // 0 would be inserted after 2 => at r+1
  EXPECT_EQ(binary_search(ptrs, 0, 1, 3, Aleph::greater<int>()), 4);
}
 
TEST(SortUtilsCountingSort, basic_sort_by_identity)
{
  Array<size_t> sa = Array<size_t>::create(5);
  Array<size_t> tmp = Array<size_t>::create(5);
  sa[0] = 3; sa[1] = 0; sa[2] = 4; sa[3] = 1; sa[4] = 2;
 
  counting_sort_indices(sa, tmp, 5, 0, 4,
                        [](size_t idx) -> int { return static_cast<int>(idx); });
 
  for (size_t i = 0; i < 5; ++i)
    EXPECT_EQ(sa[i], i);
}
 
TEST(SortUtilsCountingSort, stability)
{
  // Two pairs with same key: (10,key=1) and (20,key=1)
  // Original order: indices 0(key=2), 1(key=1), 2(key=1), 3(key=0)
  Array<size_t> sa = Array<size_t>::create(4);
  Array<size_t> tmp = Array<size_t>::create(4);
  sa[0] = 0; sa[1] = 1; sa[2] = 2; sa[3] = 3;
 
  std::array<int, 4> keys = {2, 1, 1, 0};
  counting_sort_indices(sa, tmp, 4, 0, 2,
                        [&](size_t idx) -> int { return keys[idx]; });
 
  // Expected: 3(key=0), 1(key=1), 2(key=1), 0(key=2)
  EXPECT_EQ(sa[0], 3u);
  EXPECT_EQ(sa[1], 1u);  // stable: 1 before 2
  EXPECT_EQ(sa[2], 2u);
  EXPECT_EQ(sa[3], 0u);
}
 
TEST(SortUtilsCountingSort, negative_keys)
{
  Array<size_t> sa = Array<size_t>::create(4);
  Array<size_t> tmp = Array<size_t>::create(4);
  sa[0] = 0; sa[1] = 1; sa[2] = 2; sa[3] = 3;
 
  std::array<int, 4> keys = {0, -1, 2, -2};
  counting_sort_indices(sa, tmp, 4, -2, 2,
                        [&](size_t idx) -> int { return keys[idx]; });
 
  // Sorted by key: 3(-2), 1(-1), 0(0), 2(2)
  EXPECT_EQ(sa[0], 3u);
  EXPECT_EQ(sa[1], 1u);
  EXPECT_EQ(sa[2], 0u);
  EXPECT_EQ(sa[3], 2u);
}
 
TEST(SortUtilsCountingSort, single_element)
{
  Array<size_t> sa = Array<size_t>::create(1);
  Array<size_t> tmp = Array<size_t>::create(1);
  sa[0] = 42;
 
  counting_sort_indices(sa, tmp, 1, 0, 0,
                        [](size_t) -> int { return 0; });
  EXPECT_EQ(sa[0], 42u);
}
 
TEST(SortUtilsCountingSort, empty)
{
  Array<size_t> sa;
  Array<size_t> tmp;
  counting_sort_indices(sa, tmp, 0, 0, 0,
                        [](size_t) -> int { return 0; });
  EXPECT_TRUE(sa.is_empty());
}
 
TEST(SortUtilsCountingSort, invalid_key_interval_throws)
{
  Array<size_t> sa = Array<size_t>::create(1);
  Array<size_t> tmp = Array<size_t>::create(1);
  sa[0] = 0;
 
  EXPECT_THROW(
    counting_sort_indices(sa, tmp, 1, 3, 2,
                          [](size_t) -> int { return 0; }),
    std::domain_error);
}
 
TEST(SortUtilsCountingSort, key_out_of_range_throws)
{
  Array<size_t> sa = Array<size_t>::create(2);
  Array<size_t> tmp = Array<size_t>::create(2);
  sa[0] = 0;
  sa[1] = 1;
 
  EXPECT_THROW(
    counting_sort_indices(sa, tmp, 2, 0, 1,
                          [](size_t idx) -> int { return idx == 0 ? 0 : 2; }),
    std::out_of_range);
}
 
TEST(SortUtilsCountingSort, insufficient_buffers_throw)
{
  Array<size_t> sa = Array<size_t>::create(1);
  Array<size_t> tmp = Array<size_t>::create(1);
  sa[0] = 0;
 
  EXPECT_THROW(
    counting_sort_indices(sa, tmp, 2, 0, 1,
                          [](size_t idx) -> int { return static_cast<int>(idx); }),
    std::out_of_range);
}
 
TEST(SortUtilsCountingSortGeneric, dynarray_signed_with_negatives)
{
  auto a = make_dynarray({5, -2, 3, -2, 0, 9, -10});
  counting_sort(a);
  EXPECT_EQ(a(0), -10);
  EXPECT_EQ(a(1), -2);
  EXPECT_EQ(a(2), -2);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsCountingSortGeneric, array_unsigned_values)
{
  Array<unsigned int> a;
  for (unsigned int x : {7u, 0u, 3u, 7u, 1u, 2u})
    a.append(x);
 
  counting_sort(a);
  EXPECT_EQ(a(0), 0u);
  EXPECT_EQ(a(1), 1u);
  EXPECT_EQ(a(2), 2u);
  EXPECT_EQ(a(3), 3u);
  EXPECT_EQ(a(4), 7u);
  EXPECT_EQ(a(5), 7u);
}
 
TEST(SortUtilsCountingSortGeneric, raw_pointer_and_nullptr_contract)
{
  int a[] = {4, 1, 3, 0, 2};
  counting_sort(a, sizeof(a) / sizeof(a[0]));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
 
  EXPECT_THROW((counting_sort<int>(nullptr, 1)), std::invalid_argument);
  EXPECT_NO_THROW((counting_sort<int>(nullptr, 0)));
}
 
TEST(SortUtilsCountingSortGeneric, c_array_overload)
{
  int a[] = {5, 1, 4, 2, 3, 0};
  counting_sort(a);
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsCountingSortGeneric, dynarray_support)
{
  auto a = make_dynarray({9, -1, 3, 0, -1, 2});
  counting_sort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
  ASSERT_EQ(a.size(), 6u);
  EXPECT_EQ(a(0), -1);
  EXPECT_EQ(a(1), -1);
  EXPECT_EQ(a(5), 9);
}
 
TEST(SortUtilsCountingSortGeneric, empty_and_singleton)
{
  DynArray<int> d;
  counting_sort(d);
  EXPECT_TRUE(d.is_empty());
 
  Array<int> a;
  a.append(7);
  counting_sort(a);
  ASSERT_EQ(a.size(), 1u);
  EXPECT_EQ(a(0), 7);
}
 
TEST(SortUtilsCountingSortGeneric, dynlist_support)
{
  DynList<int> l = make_dynlist({4, -1, 3, 0, -1, 2});
  counting_sort(l);
 
  std::array<int, 6> expected = {-1, -1, 0, 2, 3, 4};
  size_t i = 0;
  for (DynList<int>::Iterator it(l); it.has_curr(); it.next(), ++i)
    EXPECT_EQ(it.get_curr(), expected[i]);
  EXPECT_EQ(i, expected.size());
}
 
TEST(SortUtilsCountingSortGeneric, dynlist_preserves_nodes)
{
  DynList<int> l = make_dynlist({4, -1, 3, 0, -1, 2});
  const auto before = dynlist_node_addresses(l);
  counting_sort(l);
  const auto after = dynlist_node_addresses(l);
  expect_same_dynarray(before, after);
}
 
TEST(SortUtilsCountingSortGeneric, dyndlist_support)
{
  DynDlist<int> l = make_dyndlist({7, 3, 7, 1, 0, -2});
  counting_sort(l);
 
  std::array<int, 6> expected = {-2, 0, 1, 3, 7, 7};
  size_t i = 0;
  for (DynDlist<int>::Iterator it(l); it.has_curr(); it.next(), ++i)
    EXPECT_EQ(it.get_curr(), expected[i]);
  EXPECT_EQ(i, expected.size());
}
 
TEST(SortUtilsCountingSortGeneric, dyndlist_preserves_nodes)
{
  DynDlist<int> l = make_dyndlist({7, 3, 7, 1, 0, -2});
  const auto before = dyndlist_node_addresses(l);
  counting_sort(l);
  const auto after = dyndlist_node_addresses(l);
  expect_same_dynarray(before, after);
}
 
TEST(SortUtilsCountingSortGeneric, huge_range_throws)
{
  DynArray<unsigned long long> a;
  a.reserve(2);
  a(0) = 0ull;
  a(1) = std::numeric_limits<unsigned long long>::max();
  EXPECT_THROW(counting_sort(a), std::runtime_error);
}
 
TEST(SortUtilsRadixSort, dynarray_signed_basic)
{
  auto a = make_dynarray({170, 45, 75, 90, 802, 24, 2, 66});
  radix_sort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsRadixSort, dynarray_with_negatives)
{
  auto a = make_dynarray({0, -1, 5, -10, 3, -1, 2});
  radix_sort(a);
  EXPECT_EQ(a(0), -10);
  EXPECT_EQ(a(1), -1);
  EXPECT_EQ(a(2), -1);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsRadixSort, array_container)
{
  Array<int> a;
  for (int x : {9, 1, 8, 2, 7, 3, 6, 4, 5, 0})
    a.append(x);
 
  radix_sort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsRadixSort, raw_pointer)
{
  int a[] = {9, 1, 8, 2, 7, 3, 6, 4, 5, 0};
  radix_sort(a, sizeof(a) / sizeof(a[0]));
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsRadixSort, c_array_overload)
{
  int a[] = {9, 1, 8, 2, 7, 3, 6, 4, 5, 0};
  radix_sort(a);
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(SortUtilsRadixSort, raw_pointer_nullptr_contract)
{
  EXPECT_THROW((radix_sort<int>(nullptr, 1)), std::invalid_argument);
  EXPECT_NO_THROW((radix_sort<int>(nullptr, 0)));
}
 
TEST(SortUtilsRadixSort, dynlist_support)
{
  DynList<int> l = make_dynlist({3, -1, 2, -5, 0, 3});
  radix_sort(l);
 
  std::array<int, 6> expected = {-5, -1, 0, 2, 3, 3};
  size_t i = 0;
  for (DynList<int>::Iterator it(l); it.has_curr(); it.next(), ++i)
    EXPECT_EQ(it.get_curr(), expected[i]);
  EXPECT_EQ(i, expected.size());
}
 
TEST(SortUtilsRadixSort, dynlist_preserves_nodes)
{
  DynList<int> l = make_dynlist({3, -1, 2, -5, 0, 3});
  const auto before = dynlist_node_addresses(l);
  radix_sort(l);
  const auto after = dynlist_node_addresses(l);
  expect_same_dynarray(before, after);
}
 
TEST(SortUtilsRadixSort, dyndlist_support)
{
  DynDlist<int> l = make_dyndlist({10, -2, 7, 0, -2, 1});
  radix_sort(l);
 
  std::array<int, 6> expected = {-2, -2, 0, 1, 7, 10};
  size_t i = 0;
  for (DynDlist<int>::Iterator it(l); it.has_curr(); it.next(), ++i)
    EXPECT_EQ(it.get_curr(), expected[i]);
  EXPECT_EQ(i, expected.size());
}
 
TEST(SortUtilsRadixSort, dyndlist_preserves_nodes)
{
  DynDlist<int> l = make_dyndlist({10, -2, 7, 0, -2, 1});
  const auto before = dyndlist_node_addresses(l);
  radix_sort(l);
  const auto after = dyndlist_node_addresses(l);
  expect_same_dynarray(before, after);
}
 
TEST(SortUtilsRadixSort, signed_extremes)
{
  DynArray<int> a;
  a.reserve(6);
  a(0) = std::numeric_limits<int>::max();
  a(1) = 0;
  a(2) = std::numeric_limits<int>::min();
  a(3) = -1;
  a(4) = std::numeric_limits<int>::max();
  a(5) = std::numeric_limits<int>::min();
 
  radix_sort(a);
 
  EXPECT_EQ(a(0), std::numeric_limits<int>::min());
  EXPECT_EQ(a(1), std::numeric_limits<int>::min());
  EXPECT_EQ(a(4), std::numeric_limits<int>::max());
  EXPECT_EQ(a(5), std::numeric_limits<int>::max());
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsRadixSort, unsigned_values)
{
  Array<unsigned int> a;
  for (unsigned int x : {std::numeric_limits<unsigned int>::max(),
                         0u, 10u, 1u, 1024u, 10u})
    a.append(x);
 
  radix_sort(a);
 
  EXPECT_EQ(a(0), 0u);
  EXPECT_EQ(a(1), 1u);
  EXPECT_EQ(a(2), 10u);
  EXPECT_EQ(a(3), 10u);
  EXPECT_EQ(a(a.size() - 1), std::numeric_limits<unsigned int>::max());
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(SortUtilsRadixSort, empty_and_singleton)
{
  DynArray<int> d;
  radix_sort(d);
  EXPECT_EQ(d.size(), 0u);
 
  Array<int> a;
  a.append(7);
  radix_sort(a);
  ASSERT_EQ(a.size(), 1u);
  EXPECT_EQ(a(0), 7);
}
 
TEST(SortUtilsRandomSelect, duplicates_three_way_partition)
{
  DynArray<int> v = make_dynarray({9, 2, 4, 7, 3, 7, 10, 2, 7, 1, 8, 7, 7, 7, 7});
  std::vector<int> expected = {9, 2, 4, 7, 3, 7, 10, 2, 7, 1, 8, 7, 7, 7, 7};
  std::sort(expected.begin(), expected.end());
 
  for (size_t i = 0; i < v.size(); ++i)
    {
      DynArray<int> copy = v;
      int res = Aleph::random_select(&copy(0), static_cast<long>(i), static_cast<long>(copy.size()), std::less<int>());
      EXPECT_EQ(res, expected[i]) << "Mismatch at index " << i;
    }
}
 
TEST(SortUtilsRandomSelect, identical_elements)
{
  DynArray<int> v;
  for (int i = 0; i < 100; ++i)
    v.append(42);
 
  for (size_t i = 0; i < v.size(); i += 10)
    {
      DynArray<int> copy = v;
      int res = Aleph::random_select(&copy(0), static_cast<long>(i), static_cast<long>(copy.size()), std::less<int>());
      EXPECT_EQ(res, 42) << "Mismatch at index " << i;
    }
}
 
TEST(SortUtilsRandomSelect, sorted_and_reverse_sorted)
{
  DynArray<int> v;
  for (int i = 0; i < 50; ++i)
    v.append(i);
 
  DynArray<int> rev;
  for (int i = 49; i >= 0; --i)
    rev.append(i);
 
  for (size_t i = 0; i < v.size(); i += 5)
    {
      DynArray<int> copy_v = v;
      DynArray<int> copy_rev = rev;
      
      EXPECT_EQ(Aleph::random_select(&copy_v(0), static_cast<long>(i), static_cast<long>(copy_v.size()), std::less<int>()), static_cast<int>(i));
      EXPECT_EQ(Aleph::random_select(&copy_rev(0), static_cast<long>(i), static_cast<long>(copy_rev.size()), std::less<int>()), static_cast<int>(i));
    }
}
 
TEST(SortUtilsRandomSelect, RandomizedSeededProperty)
{
  std::mt19937 gen(42);
  for (int iter = 0; iter < 100; ++iter)
    {
      const size_t N = std::uniform_int_distribution<size_t>(1, 200)(gen);
      DynArray<int> a;
      std::vector<int> expected;
      for (size_t i = 0; i < N; ++i)
        {
          int val = std::uniform_int_distribution<int>(-1000, 1000)(gen);
          a.append(val);
          expected.push_back(val);
        }
      std::sort(expected.begin(), expected.end());
 
      const long k = std::uniform_int_distribution<long>(0, static_cast<long>(N) - 1)(gen);
      DynArray<int> copy = a;
      int res = Aleph::random_select(&copy(0), k, static_cast<long>(N), std::less<int>());
      EXPECT_EQ(res, expected[k]) << "Mismatch at iter " << iter << " rank " << k << " N " << N;
    }
}
 
// ================================================================
//                   Bucket Sort Tests
// ================================================================
 
TEST(BucketSort, float_uniform)
{
  constexpr size_t N = 500;
  DynArray<float> a;
  a.reserve(N);
  std::mt19937 gen(42);
  std::uniform_real_distribution<float> dist(0.0f, 1.0f);
  for (size_t i = 0; i < N; ++i)
    a(i) = dist(gen);
 
  bucket_sort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(BucketSort, float_with_negatives)
{
  constexpr size_t N = 300;
  DynArray<float> a;
  a.reserve(N);
  std::mt19937 gen(123);
  std::uniform_real_distribution<float> dist(-100.0f, 100.0f);
  for (size_t i = 0; i < N; ++i)
    a(i) = dist(gen);
 
  bucket_sort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(BucketSort, double_support)
{
  constexpr size_t N = 200;
  DynArray<double> a;
  a.reserve(N);
  std::mt19937 gen(77);
  std::uniform_real_distribution<double> dist(-50.0, 50.0);
  for (size_t i = 0; i < N; ++i)
    a(i) = dist(gen);
 
  bucket_sort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(BucketSort, descending_order)
{
  constexpr size_t N = 100;
  DynArray<double> a;
  a.reserve(N);
  std::mt19937 gen(99);
  std::uniform_real_distribution<double> dist(-10.0, 10.0);
  for (size_t i = 0; i < N; ++i)
    a(i) = dist(gen);
 
  bucket_sort(a, Aleph::greater<double>());
  for (size_t i = 1; i < N; ++i)
    ASSERT_GE(a(i - 1), a(i)) << "Failed at index " << i << " values: " << a(i-1) << ", " << a(i);
}
 
TEST(BucketSort, custom_bucket_key)
{
  int a[] = {95, 23, 67, 12, 45, 78, 34, 56, 89, 1};
  const size_t n = sizeof(a) / sizeof(a[0]);
  const size_t num_buckets = 10;
 
  auto key = [](const int & val) -> size_t
  {
    return static_cast<size_t>(val / 10);
  };
 
  bucket_sort(a, n, num_buckets, key);
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(BucketSort, custom_bucket_key_move_only_pointer)
{
  struct MoveOnlyInt
  {
    int value = 0;
 
    MoveOnlyInt() = default;
    explicit MoveOnlyInt(const int v) : value(v) {}
    MoveOnlyInt(const MoveOnlyInt &) = delete;
    MoveOnlyInt & operator = (const MoveOnlyInt &) = delete;
    MoveOnlyInt(MoveOnlyInt &&) noexcept = default;
    MoveOnlyInt & operator = (MoveOnlyInt &&) noexcept = default;
  };
 
  static_assert(not std::is_copy_constructible_v<MoveOnlyInt>);
  static_assert(not std::is_copy_assignable_v<MoveOnlyInt>);
 
  MoveOnlyInt a[] = {
    MoveOnlyInt(7), MoveOnlyInt(1), MoveOnlyInt(4), MoveOnlyInt(0),
    MoveOnlyInt(6), MoveOnlyInt(2), MoveOnlyInt(5), MoveOnlyInt(3)
  };
  const size_t n = sizeof(a) / sizeof(a[0]);
  const size_t num_buckets = 4;
  auto key = [](const MoveOnlyInt & x) -> size_t
  {
    return static_cast<size_t>(x.value / 2);
  };
  auto cmp = [](const MoveOnlyInt & lhs, const MoveOnlyInt & rhs)
  {
    return lhs.value < rhs.value;
  };
 
  bucket_sort(a, n, num_buckets, key, cmp);
 
  for (size_t i = 1; i < n; ++i)
    ASSERT_LE(a[i - 1].value, a[i].value);
}
 
TEST(BucketSort, dynarray_support)
{
  constexpr size_t N = 100;
  DynArray<double> a;
  a.reserve(N);
  std::mt19937 gen(55);
  std::uniform_real_distribution<double> dist(0.0, 1.0);
  for (size_t i = 0; i < N; ++i)
    a(i) = dist(gen);
 
  bucket_sort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(BucketSort, array_support)
{
  Array<double> a;
  std::mt19937 gen(99);
  std::uniform_real_distribution<double> dist(-10.0, 10.0);
  for (size_t i = 0; i < 50; ++i)
    a.append(dist(gen));
 
  bucket_sort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(BucketSort, c_array_overload)
{
  double a[] = {3.5, 1.2, 4.8, 0.3, 2.7, 1.9, 4.1, 0.1};
  bucket_sort(a);
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(BucketSort, dynlist_support)
{
  DynList<double> l;
  l.append(3.5);
  l.append(1.2);
  l.append(4.8);
  l.append(0.3);
  l.append(2.7);
 
  bucket_sort(l);
 
  double prev = -std::numeric_limits<double>::infinity();
  for (DynList<double>::Iterator it(l); it.has_curr(); it.next())
    {
      EXPECT_GE(it.get_curr(), prev);
      prev = it.get_curr();
    }
}
 
TEST(BucketSort, empty_and_singleton)
{
  DynArray<float> d;
  bucket_sort(d);
  EXPECT_EQ(d.size(), 0u);
 
  DynArray<float> s;
  s.reserve(1);
  s(0) = 42.0f;
  bucket_sort(s);
  ASSERT_EQ(s.size(), 1u);
  EXPECT_FLOAT_EQ(s(0), 42.0f);
}
 
TEST(BucketSort, all_equal)
{
  constexpr size_t N = 50;
  DynArray<float> a;
  a.reserve(N);
  for (size_t i = 0; i < N; ++i)
    a(i) = 7.7f;
 
  bucket_sort(a);
  for (size_t i = 0; i < N; ++i)
    EXPECT_FLOAT_EQ(a(i), 7.7f);
}
 
TEST(BucketSort, reverse_sorted_input)
{
  constexpr size_t N = 100;
  DynArray<double> a;
  a.reserve(N);
  for (size_t i = 0; i < N; ++i)
    a(i) = static_cast<double>(N - i);
 
  bucket_sort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(BucketSort, null_pointer_contract)
{
  EXPECT_THROW((bucket_sort<float>(nullptr, 1)), std::invalid_argument);
  EXPECT_NO_THROW((bucket_sort<float>(nullptr, 0)));
}
 
TEST(BucketSort, stability)
{
  // Records with same bucket should preserve relative order
  struct Record
  {
    int group;
    int seq;
  };
 
  Record data[] = {{0, 0}, {2, 1}, {0, 2}, {1, 3}, {2, 4}, {1, 5}};
  const size_t n = sizeof(data) / sizeof(data[0]);
  const size_t num_buckets = 3;
 
  auto key = [](const Record & r) -> size_t { return r.group; };
  auto cmp = [](const Record & a, const Record & b) { return a.group < b.group; };
 
  bucket_sort(data, n, num_buckets, key, cmp);
 
  // Verify sorted by group
  for (size_t i = 1; i < n; ++i)
    ASSERT_LE(data[i - 1].group, data[i].group);
 
  // Verify stability: within same group, original order preserved
  // Group 0: seq 0, 2
  EXPECT_EQ(data[0].seq, 0);
  EXPECT_EQ(data[1].seq, 2);
  // Group 1: seq 3, 5
  EXPECT_EQ(data[2].seq, 3);
  EXPECT_EQ(data[3].seq, 5);
  // Group 2: seq 1, 4
  EXPECT_EQ(data[4].seq, 1);
  EXPECT_EQ(data[5].seq, 4);
}
 
 
TEST(BucketSort, zero_buckets)
{
  int a[] = {3, 1, 2};
  const size_t n = 3;
  const size_t num_buckets = 0;
  auto key = [](const int &) -> size_t { return 0; };
 
  // Zero buckets with n >= 2 must throw domain_error
  EXPECT_THROW(bucket_sort(a, n, num_buckets, key), std::domain_error);
}
 
// ================================================================
//                      Timsort Tests
// ================================================================
 
TEST(Timsort, already_sorted)
{
  constexpr size_t N = 200;
  DynArray<int> a;
  a.reserve(N);
  for (size_t i = 0; i < N; ++i)
    a(i) = static_cast<int>(i);
 
  timsort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, reverse_sorted)
{
  constexpr size_t N = 200;
  DynArray<int> a;
  a.reserve(N);
  for (size_t i = 0; i < N; ++i)
    a(i) = static_cast<int>(N - i);
 
  timsort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, random_small)
{
  int a[] = {5, 3, 8, 1, 9, 2, 7, 4, 6, 0};
  timsort(static_cast<int*>(a), size_t{10});
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(Timsort, random_large)
{
  constexpr size_t N = 10000;
  DynArray<int> a;
  a.reserve(N);
  std::mt19937 gen(42);
  std::uniform_int_distribution<int> dist(-1000000, 1000000);
  for (size_t i = 0; i < N; ++i)
    a(i) = dist(gen);
 
  timsort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, perf_large)
{
  if (not std::getenv("ENABLE_PERF_TESTS"))
    GTEST_SKIP() << "Skipping perf test (set ENABLE_PERF_TESTS to enable)";
 
  constexpr size_t N = 100000;
  DynArray<int> a;
  a.reserve(N);
  std::mt19937 gen(42);
  std::uniform_int_distribution<int> dist(-1000000, 1000000);
  for (size_t i = 0; i < N; ++i)
    a(i) = dist(gen);
 
  auto start = std::chrono::steady_clock::now();
  timsort(a);
  auto end = std::chrono::steady_clock::now();
  
  auto duration = std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count();
  
  long max_ms = 500;
  if (const char * env_ms = std::getenv("TIMSORT_MAX_MS"))
    max_ms = std::atol(env_ms);
 
  EXPECT_LE(duration, max_ms) << "Timsort performance regression detected";
 
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, all_equal)
{
  constexpr size_t N = 100;
  DynArray<int> a;
  a.reserve(N);
  for (size_t i = 0; i < N; ++i)
    a(i) = 42;
 
  timsort(a);
  for (size_t i = 0; i < N; ++i)
    EXPECT_EQ(a(i), 42);
}
 
TEST(Timsort, two_sorted_halves)
{
  constexpr size_t N = 200;
  DynArray<int> a;
  a.reserve(N);
  // First half: 0, 2, 4, ... 198
  for (size_t i = 0; i < N / 2; ++i)
    a(i) = static_cast<int>(i * 2);
  // Second half: 1, 3, 5, ... 199
  for (size_t i = N / 2; i < N; ++i)
    a(i) = static_cast<int>((i - N / 2) * 2 + 1);
 
  timsort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, custom_comparator)
{
  constexpr size_t N = 50;
  DynArray<int> a;
  a.reserve(N);
  std::mt19937 gen(99);
  for (size_t i = 0; i < N; ++i)
    a(i) = static_cast<int>(gen() % 1000);
 
  timsort(a, Aleph::greater<int>());
  for (size_t i = 1; i < N; ++i)
    ASSERT_GE(a(i - 1), a(i));
}
 
TEST(Timsort, dynarray_support)
{
  auto a = make_dynarray({9, 1, 8, 2, 7, 3, 6, 4, 5, 0});
  timsort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, array_support)
{
  Array<int> a;
  for (int x : {9, 1, 8, 2, 7, 3, 6, 4, 5, 0})
    a.append(x);
 
  timsort(a);
  for (size_t i = 1; i < a.size(); ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, c_array_overload)
{
  int a[] = {5, 3, 8, 1, 9, 2, 7, 4, 6, 0};
  timsort(a);
  EXPECT_TRUE(std::is_sorted(std::begin(a), std::end(a)));
}
 
TEST(Timsort, dynlist_support)
{
  DynList<int> l = make_dynlist({5, 3, 8, 1, 9, 2, 7, 4, 6, 0});
  timsort(l);
 
  int prev = std::numeric_limits<int>::min();
  for (DynList<int>::Iterator it(l); it.has_curr(); it.next())
    {
      EXPECT_GE(it.get_curr(), prev);
      prev = it.get_curr();
    }
}
 
TEST(Timsort, empty_and_singleton)
{
  DynArray<int> d;
  timsort(d);
  EXPECT_EQ(d.size(), 0u);
 
  Array<int> a;
  a.append(7);
  timsort(a);
  ASSERT_EQ(a.size(), 1u);
  EXPECT_EQ(a(0), 7);
}
 
TEST(Timsort, null_pointer_contract)
{
  EXPECT_THROW((timsort<int>(nullptr, 1)), std::invalid_argument);
  EXPECT_NO_THROW((timsort<int>(nullptr, 0)));
}
 
TEST(Timsort, stability)
{
  struct Record
  {
    int key;
    int seq; // original order
    bool operator<(const Record & rhs) const { return key < rhs.key; }
  };
 
  Record data[] = {
    {3, 0}, {1, 1}, {4, 2}, {1, 3}, {5, 4},
    {9, 5}, {2, 6}, {6, 7}, {5, 8}, {3, 9}
  };
  const size_t n = sizeof(data) / sizeof(data[0]);
 
  auto cmp = [](const Record & a, const Record & b) { return a.key < b.key; };
  timsort(data, n, cmp);
 
  // Verify sorted by key
  for (size_t i = 1; i < n; ++i)
    ASSERT_LE(data[i - 1].key, data[i].key);
 
  // Verify stability: equal keys preserve original seq order
  for (size_t i = 1; i < n; ++i)
    if (data[i - 1].key == data[i].key)
      EXPECT_LT(data[i - 1].seq, data[i].seq)
        << "Stability violated at index " << i;
}
 
TEST(Timsort, string_sort)
{
  Array<std::string> a;
  a.append("banana");
  a.append("apple");
  a.append("cherry");
  a.append("date");
  a.append("apricot");
 
  timsort(a, Aleph::less<std::string>());
 
  EXPECT_EQ(a(0), "apple");
  EXPECT_EQ(a(1), "apricot");
  EXPECT_EQ(a(2), "banana");
  EXPECT_EQ(a(3), "cherry");
  EXPECT_EQ(a(4), "date");
}
 
TEST(Timsort, nearly_sorted)
{
  constexpr size_t N = 500;
  DynArray<int> a;
  a.reserve(N);
  for (size_t i = 0; i < N; ++i)
    a(i) = static_cast<int>(i);
 
  // Introduce a few inversions
  std::mt19937 gen(12);
  for (int k = 0; k < 10; ++k)
    {
      size_t i = gen() % N;
      size_t j = gen() % N;
      std::swap(a(i), a(j));
    }
 
  timsort(a);
  for (size_t i = 1; i < N; ++i)
    ASSERT_LE(a(i - 1), a(i));
}
 
TEST(Timsort, range_overload)
{
  int a[] = {9, 5, 3, 8, 1, 7, 2, 6, 4, 0};
  // Sort only the subrange [2, 7] (inclusive)
  timsort(a, 2L, 7L);
 
  // a[2..7] should be sorted
  for (int i = 3; i <= 7; ++i)
    ASSERT_LE(a[i - 1], a[i]);
 
  // Elements outside the range should be unchanged
  EXPECT_EQ(a[0], 9);
  EXPECT_EQ(a[1], 5);
  EXPECT_EQ(a[8], 4);
  EXPECT_EQ(a[9], 0);
}
 
TEST(Timsort, compute_minrun)
{
  using timsort_detail::compute_minrun;
 
  // n < 64: minrun == n
  EXPECT_EQ(compute_minrun(1), 1u);
  EXPECT_EQ(compute_minrun(32), 32u);
  EXPECT_EQ(compute_minrun(63), 63u);
 
  // n == 64: minrun == 32
  EXPECT_EQ(compute_minrun(64), 32u);
 
  // minrun should always be in [32, 64] for n >= 64
  for (size_t n = 64; n < 10000; ++n)
    {
      const size_t mr = compute_minrun(n);
      EXPECT_GE(mr, 32u) << "n=" << n;
      EXPECT_LE(mr, 64u) << "n=" << n;
    }
}
 
} // namespace