arrayheap_algos.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
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  The above copyright notice and this permission notice shall be included in all
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  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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*/
 
 
#include <algorithm>
#include <ranges>
#include <vector>
 
#include <gtest/gtest.h>
 
#include <tpl_arrayHeap.H>
 
using namespace Aleph;
using namespace testing;
 
static bool is_min_heap(const std::vector<int> &v)
{
  if (v.empty())
    return true;
 
  std::vector<int> tmp(v.size() + 1);
  for (size_t i = 0; i < v.size(); ++i)
    tmp[i + 1] = v[i];
 
  Aleph::less<int> cmp;
  return valid_heap(tmp.data(), 1, v.size(), cmp);
}
 
TEST(ArrayHeapAlgos, ValidHeapDetectsHeapAndNonHeap)
{
  {
    std::vector<int> heap_like{1, 3, 2, 7, 5, 4};
    EXPECT_TRUE(is_min_heap(heap_like));
  }
 
  {
    std::vector<int> not_heap{3, 1, 2};
    EXPECT_FALSE(is_min_heap(not_heap));
  }
}
 
TEST(ArrayHeapAlgos, SiftUpRestoresHeapAfterInsertAtEnd)
{
  // Start from a valid min-heap of size 3: [1, 3, 2]
  int arr[5] = {0, 1, 3, 2, 0};
  Aleph::less<int> cmp;
 
  // Insert a smaller item at the end and sift it up
  arr[4] = 0;
  int &ref = sift_up(arr, 1, 4, cmp);
 
  EXPECT_EQ(ref, 0);
  EXPECT_TRUE(valid_heap(arr, 1, 4, cmp));
  EXPECT_EQ(arr[1], 0);
}
 
TEST(ArrayHeapAlgos, SiftDownRestoresHeapAfterRootViolation)
{
  // A min-heap of 5 elements would have 1 at root, but we break it.
  int arr[6] = {0, 9, 1, 2, 3, 4};
  Aleph::less<int> cmp;
 
  EXPECT_FALSE(valid_heap(arr, 1, 5, cmp));
  sift_down(arr, 1, 5, cmp);
  EXPECT_TRUE(valid_heap(arr, 1, 5, cmp));
  EXPECT_EQ(arr[1], 1);
}
 
TEST(ArrayHeapAlgos, SiftDownUpRestoresHeapAfterInternalUpdate)
{
  // Start with a valid heap
  int arr[8] = {0, 1, 3, 2, 7, 5, 4, 8};
  Aleph::less<int> cmp;
  ASSERT_TRUE(valid_heap(arr, 1, 7, cmp));
 
  // Make an internal node very small; it should bubble up.
  arr[6] = 0;
  sift_down_up(arr, 1, 6, 7, cmp);
  EXPECT_TRUE(valid_heap(arr, 1, 7, cmp));
  EXPECT_EQ(arr[1], 0);
 
  // Make an internal node very large; it should sink.
  arr[2] = 100;
  sift_down_up(arr, 1, 2, 7, cmp);
  EXPECT_TRUE(valid_heap(arr, 1, 7, cmp));
}
 
TEST(ArrayHeapAlgos, HeapsortMatchesStdSort)
{
  std::vector<int> v{5, 1, 4, 2, 8, 0, 3, 7, 6, 9};
  std::vector<int> expected = v;
  std::sort(expected.begin(), expected.end());
 
  heapsort(v.data(), v.size());
  EXPECT_EQ(v, expected);
}
 
TEST(ArrayHeapAlgos, FasterHeapsortMatchesStdSort)
{
  std::vector<int> v{12, -1, 5, 5, 3, 99, 0, -10, 7, 2, 4};
  std::vector<int> expected = v;
  std::sort(expected.begin(), expected.end());
 
  faster_heapsort(v.data(), v.size());
  EXPECT_EQ(v, expected);
}