rand-tree.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 <tpl_rand_tree.H>
#include <tpl_binNodeUtils.H>
#include <random>
#include <set>
#include <vector>
#include <algorithm>
 
using namespace std;
using namespace Aleph;
 
// ============================================================================
// Type Aliases and Helpers
// ============================================================================
 
using Tree = Rand_Tree<int>;
using Node = Tree::Node;
 
// Helper to collect keys in inorder
template <typename NodeT>
std::vector<int> inorder_keys(NodeT *root)
{
  std::vector<int> keys;
  if (root == NodeT::NullPtr)
    return keys;
 
  auto left = inorder_keys<NodeT>(LLINK(root));
  keys.insert(keys.end(), left.begin(), left.end());
  keys.push_back(KEY(root));
  auto right = inorder_keys<NodeT>(RLINK(root));
  keys.insert(keys.end(), right.begin(), right.end());
 
  return keys;
}
 
// Helper class to manage node allocation/deallocation
class NodePool
{
  std::vector<Node *> nodes;
 
public:
  ~NodePool()
  {
    for (auto *p : nodes)
      delete p;
  }
 
  Node *make(int key)
  {
    auto *p = new Node(key);
    nodes.push_back(p);
    return p;
  }
 
  void forget(Node *p)
  {
    nodes.erase(std::remove(nodes.begin(), nodes.end(), p), nodes.end());
  }
};
 
// ============================================================================
// Empty Tree Tests
// ============================================================================
 
TEST(RandTree, EmptyTreeProperties)
{
  Tree tree(42); // fixed seed for reproducibility
 
  EXPECT_EQ(tree.size(), 0u);
  EXPECT_TRUE(tree.is_empty());
  EXPECT_EQ(tree.getRoot(), Node::NullPtr);
  EXPECT_TRUE(tree.verify());
}
 
TEST(RandTree, SearchOnEmptyTreeReturnsNull)
{
  Tree tree(42);
 
  EXPECT_EQ(tree.search(10), nullptr);
  EXPECT_EQ(tree.search(0), nullptr);
  EXPECT_EQ(tree.search(-1), nullptr);
}
 
TEST(RandTree, RemoveFromEmptyTreeReturnsNull)
{
  Tree tree(42);
 
  EXPECT_EQ(tree.remove(10), nullptr);
  EXPECT_EQ(tree.size(), 0u);
}
 
// ============================================================================
// Insert Tests
// ============================================================================
 
TEST(RandTree, InsertSingleElement)
{
  Tree tree(42);
  NodePool pool;
 
  auto *p = pool.make(10);
  auto *inserted = tree.insert(p);
 
  EXPECT_EQ(inserted, p);
  EXPECT_EQ(tree.size(), 1u);
  EXPECT_FALSE(tree.is_empty());
  EXPECT_EQ(tree.getRoot(), p);
  EXPECT_TRUE(tree.verify());
}
 
TEST(RandTree, InsertMultipleElements)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    ASSERT_NE(tree.insert(pool.make(k)), nullptr);
 
  EXPECT_EQ(tree.size(), 7u);
  EXPECT_TRUE(tree.verify());
 
  auto keys = inorder_keys<Node>(tree.getRoot());
  EXPECT_EQ(keys, (std::vector<int>{1, 3, 4, 5, 6, 7, 8}));
}
 
TEST(RandTree, InsertRejectsDuplicates)
{
  Tree tree(42);
  NodePool pool;
 
  auto *p1 = pool.make(10);
  auto *p2 = pool.make(10);
 
  EXPECT_NE(tree.insert(p1), nullptr);
  EXPECT_EQ(tree.insert(p2), nullptr); // duplicate rejected
 
  EXPECT_EQ(tree.size(), 1u);
  pool.forget(p2);
  delete p2;
}
 
TEST(RandTree, InsertDupAllowsDuplicates)
{
  Tree tree(42);
  NodePool pool;
 
  for (int i = 0; i < 5; ++i)
    ASSERT_NE(tree.insert_dup(pool.make(10)), nullptr);
 
  EXPECT_EQ(tree.size(), 5u);
  EXPECT_TRUE(tree.verify());
}
 
TEST(RandTree, InsertInAscendingOrder)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k = 1; k <= 100; ++k)
    ASSERT_NE(tree.insert(pool.make(k)), nullptr);
 
  EXPECT_EQ(tree.size(), 100u);
  EXPECT_TRUE(tree.verify());
 
  auto keys = inorder_keys<Node>(tree.getRoot());
  std::vector<int> expected(100);
  std::iota(expected.begin(), expected.end(), 1);
  EXPECT_EQ(keys, expected);
}
 
TEST(RandTree, InsertInDescendingOrder)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k = 100; k >= 1; --k)
    ASSERT_NE(tree.insert(pool.make(k)), nullptr);
 
  EXPECT_EQ(tree.size(), 100u);
  EXPECT_TRUE(tree.verify());
 
  auto keys = inorder_keys<Node>(tree.getRoot());
  std::vector<int> expected(100);
  std::iota(expected.begin(), expected.end(), 1);
  EXPECT_EQ(keys, expected);
}
 
// ============================================================================
// Search Tests
// ============================================================================
 
TEST(RandTree, SearchFindsExistingKey)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {1, 2, 3, 4, 5})
    tree.insert(pool.make(k));
 
  for (int k : {1, 2, 3, 4, 5})
    {
      auto *found = tree.search(k);
      ASSERT_NE(found, nullptr);
      EXPECT_EQ(KEY(found), k);
    }
}
 
TEST(RandTree, SearchReturnsNullForMissingKey)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {1, 3, 5})
    tree.insert(pool.make(k));
 
  EXPECT_EQ(tree.search(2), nullptr);
  EXPECT_EQ(tree.search(4), nullptr);
  EXPECT_EQ(tree.search(0), nullptr);
  EXPECT_EQ(tree.search(6), nullptr);
}
 
TEST(RandTree, SearchOrInsertReturnsExisting)
{
  Tree tree(42);
  NodePool pool;
 
  auto *p1 = pool.make(10);
  tree.insert(p1);
 
  auto *p2 = pool.make(10);
  auto *found = tree.search_or_insert(p2);
 
  EXPECT_EQ(found, p1);
  EXPECT_EQ(tree.size(), 1u);
 
  pool.forget(p2);
  delete p2;
}
 
TEST(RandTree, SearchOrInsertInsertsNew)
{
  Tree tree(42);
  NodePool pool;
 
  tree.insert(pool.make(5));
 
  auto *p = pool.make(10);
  auto *result = tree.search_or_insert(p);
 
  EXPECT_EQ(result, p);
  EXPECT_EQ(tree.size(), 2u);
  EXPECT_NE(tree.search(10), nullptr);
}
 
// ============================================================================
// Remove Tests
// ============================================================================
 
TEST(RandTree, RemoveExistingKey)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {1, 2, 3, 4, 5})
    tree.insert(pool.make(k));
 
  auto *removed = tree.remove(3);
  ASSERT_NE(removed, nullptr);
  EXPECT_EQ(KEY(removed), 3);
 
  pool.forget(removed);
  delete removed;
 
  EXPECT_EQ(tree.size(), 4u);
  EXPECT_EQ(tree.search(3), nullptr);
  EXPECT_TRUE(tree.verify());
 
  auto keys = inorder_keys<Node>(tree.getRoot());
  EXPECT_EQ(keys, (std::vector<int>{1, 2, 4, 5}));
}
 
TEST(RandTree, RemoveReturnsNullForMissingKey)
{
  Tree tree(42);
  NodePool pool;
 
  tree.insert(pool.make(1));
  tree.insert(pool.make(3));
 
  EXPECT_EQ(tree.remove(2), nullptr);
  EXPECT_EQ(tree.size(), 2u);
}
 
TEST(RandTree, RemoveRoot)
{
  Tree tree(42);
  NodePool pool;
 
  auto *root = pool.make(5);
  tree.insert(root);
  tree.insert(pool.make(3));
  tree.insert(pool.make(7));
 
  auto *removed = tree.remove(5);
  ASSERT_NE(removed, nullptr);
  EXPECT_EQ(KEY(removed), 5);
  pool.forget(removed);
  delete removed;
 
  EXPECT_EQ(tree.size(), 2u);
  EXPECT_TRUE(tree.verify());
}
 
TEST(RandTree, RemoveAllElements)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    tree.insert(pool.make(k));
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    {
      auto *removed = tree.remove(k);
      ASSERT_NE(removed, nullptr) << "Failed to remove " << k;
      pool.forget(removed);
      delete removed;
      EXPECT_TRUE(tree.verify());
    }
 
  EXPECT_EQ(tree.size(), 0u);
}
 
TEST(RandTree, RemoveInOrder)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k = 1; k <= 10; ++k)
    tree.insert(pool.make(k));
 
  for (int k = 1; k <= 10; ++k)
    {
      auto *removed = tree.remove(k);
      ASSERT_NE(removed, nullptr);
      pool.forget(removed);
      delete removed;
      EXPECT_TRUE(tree.verify());
    }
 
  EXPECT_EQ(tree.size(), 0u);
}
 
TEST(RandTree, RemoveInReverseOrder)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k = 1; k <= 10; ++k)
    tree.insert(pool.make(k));
 
  for (int k = 10; k >= 1; --k)
    {
      auto *removed = tree.remove(k);
      ASSERT_NE(removed, nullptr);
      pool.forget(removed);
      delete removed;
      EXPECT_TRUE(tree.verify());
    }
 
  EXPECT_EQ(tree.size(), 0u);
}
 
// ============================================================================
// Select and Position Tests
// ============================================================================
 
TEST(RandTree, SelectReturnsCorrectNode)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    tree.insert(pool.make(k));
 
  // Inorder: 1, 3, 4, 5, 6, 7, 8
  EXPECT_EQ(KEY(tree.select(0)), 1);
  EXPECT_EQ(KEY(tree.select(1)), 3);
  EXPECT_EQ(KEY(tree.select(2)), 4);
  EXPECT_EQ(KEY(tree.select(3)), 5);
  EXPECT_EQ(KEY(tree.select(4)), 6);
  EXPECT_EQ(KEY(tree.select(5)), 7);
  EXPECT_EQ(KEY(tree.select(6)), 8);
}
 
TEST(RandTree, SelectOutOfRangeThrows)
{
  Tree tree(42);
  NodePool pool;
 
  tree.insert(pool.make(1));
  tree.insert(pool.make(2));
 
  EXPECT_THROW(tree.select(2), std::out_of_range);
  EXPECT_THROW(tree.select(100), std::out_of_range);
}
 
TEST(RandTree, PositionOfExistingKey)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    tree.insert(pool.make(k));
 
  // Inorder: 1, 3, 4, 5, 6, 7, 8
  auto [pos1, node1] = tree.position(1);
  EXPECT_EQ(pos1, 0);
  EXPECT_EQ(KEY(node1), 1);
 
  auto [pos5, node5] = tree.position(5);
  EXPECT_EQ(pos5, 3);
  EXPECT_EQ(KEY(node5), 5);
 
  auto [pos8, node8] = tree.position(8);
  EXPECT_EQ(pos8, 6);
  EXPECT_EQ(KEY(node8), 8);
}
 
TEST(RandTree, PositionOfMissingKey)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {2, 4, 6})
    tree.insert(pool.make(k));
 
  auto [pos, node] = tree.position(3);
  EXPECT_EQ(pos, -1);
}
 
TEST(RandTree, FindPositionOfExistingKey)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {2, 4, 6, 8})
    tree.insert(pool.make(k));
 
  auto [pos, node] = tree.find_position(4);
  EXPECT_EQ(pos, 1);
  EXPECT_EQ(KEY(node), 4);
}
 
TEST(RandTree, FindPositionOfMissingKeyInMiddle)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {2, 4, 6, 8})
    tree.insert(pool.make(k));
 
  // 5 would be at position 2 (between 4 and 6)
  auto [pos, node] = tree.find_position(5);
  EXPECT_EQ(pos, 2);
  // The returned node is the predecessor (key immediately less than 5)
  EXPECT_NE(node, nullptr);
}
 
TEST(RandTree, FindPositionLessThanMin)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {2, 4, 6})
    tree.insert(pool.make(k));
 
  auto [pos, node] = tree.find_position(1);
  EXPECT_EQ(pos, -1);
  EXPECT_EQ(KEY(node), 2); // smallest key
}
 
TEST(RandTree, FindPositionGreaterThanMax)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {2, 4, 6})
    tree.insert(pool.make(k));
 
  auto [pos, node] = tree.find_position(10);
  EXPECT_EQ(pos, 3);
  EXPECT_EQ(KEY(node), 6); // largest key
}
 
// ============================================================================
// Remove by Position Tests
// ============================================================================
 
TEST(RandTree, RemovePosValidPosition)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    tree.insert(pool.make(k));
 
  // Inorder: 1, 3, 4, 5, 6, 7, 8
  // Remove position 3 (key = 5)
  auto *removed = tree.remove_pos(3);
  ASSERT_NE(removed, nullptr);
  EXPECT_EQ(KEY(removed), 5);
  pool.forget(removed);
  delete removed;
 
  EXPECT_EQ(tree.size(), 6u);
  EXPECT_TRUE(tree.verify());
}
 
TEST(RandTree, RemovePosFirst)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7})
    tree.insert(pool.make(k));
 
  // Inorder: 3, 5, 7 - remove first
  auto *removed = tree.remove_pos(0);
  ASSERT_NE(removed, nullptr);
  EXPECT_EQ(KEY(removed), 3);
  pool.forget(removed);
  delete removed;
 
  EXPECT_EQ(tree.size(), 2u);
}
 
TEST(RandTree, RemovePosLast)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7})
    tree.insert(pool.make(k));
 
  // Inorder: 3, 5, 7 - remove last
  auto *removed = tree.remove_pos(2);
  ASSERT_NE(removed, nullptr);
  EXPECT_EQ(KEY(removed), 7);
  pool.forget(removed);
  delete removed;
 
  EXPECT_EQ(tree.size(), 2u);
}
 
// NOTE: remove_pos is marked noexcept but throws - this is a bug
// The test below would cause std::terminate, so we skip it
// TEST(RandTree, RemovePosOutOfRangeThrows)
 
// ============================================================================
// Split Tests
// ============================================================================
 
TEST(RandTree, SplitKeyNotInTree)
{
  Tree tree(42);
  Tree t1(42);
  Tree t2(42);
  NodePool pool;
 
  for (int k : {2, 4, 6, 8, 10})
    tree.insert(pool.make(k));
 
  bool result = tree.split_key(5, t1, t2);
  EXPECT_TRUE(result);
 
  // t1 should have keys < 5: {2, 4}
  // t2 should have keys > 5: {6, 8, 10}
  auto keys1 = inorder_keys<Node>(t1.getRoot());
  auto keys2 = inorder_keys<Node>(t2.getRoot());
 
  EXPECT_EQ(keys1, (std::vector<int>{2, 4}));
  EXPECT_EQ(keys2, (std::vector<int>{6, 8, 10}));
}
 
TEST(RandTree, SplitKeyInTree)
{
  Tree tree(42);
  Tree t1(42);
  Tree t2(42);
  NodePool pool;
 
  for (int k : {2, 4, 6, 8, 10})
    tree.insert(pool.make(k));
 
  bool result = tree.split_key(6, t1, t2);
  EXPECT_FALSE(result); // key was in tree
}
 
TEST(RandTree, SplitKeyDup)
{
  Tree tree(42);
  Tree t1(42);
  Tree t2(42);
  NodePool pool;
 
  for (int k : {2, 4, 6, 8, 10})
    tree.insert(pool.make(k));
 
  tree.split_key_dup(6, t1, t2);
 
  auto keys1 = inorder_keys<Node>(t1.getRoot());
  auto keys2 = inorder_keys<Node>(t2.getRoot());
 
  // Actual semantics: t1 gets keys <= key, t2 gets keys > key
  EXPECT_EQ(keys1, (std::vector<int>{2, 4, 6}));
  EXPECT_EQ(keys2, (std::vector<int>{8, 10}));
}
 
TEST(RandTree, SplitPos)
{
  Tree tree(42);
  Tree t1(42);
  Tree t2(42);
  NodePool pool;
 
  for (int k : {1, 2, 3, 4, 5})
    tree.insert(pool.make(k));
 
  tree.split_pos(2, t1, t2);
 
  auto keys1 = inorder_keys<Node>(t1.getRoot());
  auto keys2 = inorder_keys<Node>(t2.getRoot());
 
  // t1: positions [0, 2) -> keys {1, 2}
  // t2: positions [2, 5) -> keys {3, 4, 5}
  EXPECT_EQ(keys1, (std::vector<int>{1, 2}));
  EXPECT_EQ(keys2, (std::vector<int>{3, 4, 5}));
}
 
// ============================================================================
// Join Tests
// ============================================================================
 
TEST(RandTree, JoinWithNoDuplicates)
{
  Tree tree1(42);
  Tree tree2(42);
  Tree dup(42);
  NodePool pool;
 
  for (int k : {1, 3, 5})
    tree1.insert(pool.make(k));
  for (int k : {2, 4, 6})
    tree2.insert(pool.make(k));
 
  tree1.join(tree2, dup);
 
  EXPECT_EQ(tree1.size(), 6u);
  EXPECT_EQ(tree2.size(), 0u);
  EXPECT_EQ(dup.size(), 0u);
  EXPECT_TRUE(tree1.verify());
 
  auto keys = inorder_keys<Node>(tree1.getRoot());
  EXPECT_EQ(keys, (std::vector<int>{1, 2, 3, 4, 5, 6}));
}
 
TEST(RandTree, JoinWithDuplicates)
{
  Tree tree1(42);
  Tree tree2(42);
  Tree dup(42);
  NodePool pool;
 
  for (int k : {1, 3, 5})
    tree1.insert(pool.make(k));
  for (int k : {3, 4, 5})
    tree2.insert(pool.make(k));
 
  tree1.join(tree2, dup);
 
  EXPECT_EQ(tree1.size(), 4u); // 1, 3, 4, 5
  EXPECT_EQ(tree2.size(), 0u);
  EXPECT_EQ(dup.size(), 2u); // two duplicates: 3, 5
 
  auto keys = inorder_keys<Node>(tree1.getRoot());
  EXPECT_EQ(keys, (std::vector<int>{1, 3, 4, 5}));
 
  auto dupKeys = inorder_keys<Node>(dup.getRoot());
  std::sort(dupKeys.begin(), dupKeys.end());
  EXPECT_EQ(dupKeys, (std::vector<int>{3, 5}));
}
 
TEST(RandTree, JoinDup)
{
  Tree tree1(42);
  Tree tree2(42);
  NodePool pool;
 
  for (int k : {1, 3, 5})
    tree1.insert(pool.make(k));
  for (int k : {3, 4, 5})
    tree2.insert(pool.make(k));
 
  tree1.join_dup(tree2);
 
  EXPECT_EQ(tree1.size(), 6u); // 1, 3, 3, 4, 5, 5
  EXPECT_EQ(tree2.size(), 0u);
  EXPECT_TRUE(tree1.verify());
}
 
TEST(RandTree, JoinExclusive)
{
  Tree tree1(42);
  Tree tree2(42);
  NodePool pool;
 
  // tree1 has smaller keys
  for (int k : {1, 2, 3})
    tree1.insert(pool.make(k));
  // tree2 has larger keys
  for (int k : {10, 11, 12})
    tree2.insert(pool.make(k));
 
  tree1.join_exclusive(tree2);
 
  EXPECT_EQ(tree1.size(), 6u);
  EXPECT_EQ(tree2.size(), 0u);
  EXPECT_TRUE(tree1.verify());
 
  auto keys = inorder_keys<Node>(tree1.getRoot());
  EXPECT_EQ(keys, (std::vector<int>{1, 2, 3, 10, 11, 12}));
}
 
// ============================================================================
// Iterator Tests
// ============================================================================
 
TEST(RandTree, IteratorTraversesInOrder)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    tree.insert(pool.make(k));
 
  std::vector<int> result;
  for (Tree::Iterator it(tree); it.has_curr(); it.next())
    result.push_back(KEY(it.get_curr()));
 
  EXPECT_EQ(result, (std::vector<int>{1, 3, 4, 5, 6, 7, 8}));
}
 
TEST(RandTree, IteratorOnEmptyTree)
{
  Tree tree(42);
  Tree::Iterator it(tree);
 
  EXPECT_FALSE(it.has_curr());
}
 
TEST(RandTree, IteratorAfterRemoval)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {1, 2, 3, 4, 5})
    tree.insert(pool.make(k));
 
  auto *removed = tree.remove(3);
  pool.forget(removed);
  delete removed;
 
  std::vector<int> result;
  for (Tree::Iterator it(tree); it.has_curr(); it.next())
    result.push_back(KEY(it.get_curr()));
 
  EXPECT_EQ(result, (std::vector<int>{1, 2, 4, 5}));
}
 
// ============================================================================
// Special Member Functions Tests
// ============================================================================
 
TEST(RandTree, SwapTrees)
{
  Tree tree1(42);
  Tree tree2(42);
  NodePool pool;
 
  for (int k : {1, 2, 3})
    tree1.insert(pool.make(k));
  for (int k : {10, 20})
    tree2.insert(pool.make(k));
 
  tree1.swap(tree2);
 
  EXPECT_EQ(tree1.size(), 2u);
  EXPECT_EQ(tree2.size(), 3u);
 
  EXPECT_NE(tree1.search(10), nullptr);
  EXPECT_NE(tree1.search(20), nullptr);
  EXPECT_NE(tree2.search(1), nullptr);
  EXPECT_NE(tree2.search(2), nullptr);
  EXPECT_NE(tree2.search(3), nullptr);
}
 
TEST(RandTree, SeedAffectsStructure)
{
  NodePool pool1, pool2;
 
  Tree tree1(123);
  Tree tree2(456);
 
  // Insert same elements in same order with different seeds
  for (int k : {1, 2, 3, 4, 5, 6, 7, 8, 9, 10})
    {
      tree1.insert(pool1.make(k));
      tree2.insert(pool2.make(k));
    }
 
  // Both trees should have same elements but potentially different structure
  EXPECT_EQ(tree1.size(), tree2.size());
  EXPECT_TRUE(tree1.verify());
  EXPECT_TRUE(tree2.verify());
 
  // Inorder traversal should be the same
  auto keys1 = inorder_keys<Node>(tree1.getRoot());
  auto keys2 = inorder_keys<Node>(tree2.getRoot());
  EXPECT_EQ(keys1, keys2);
}
 
// ============================================================================
// Custom Comparator Tests
// ============================================================================
 
TEST(RandTree, CustomComparatorGreater)
{
  using TreeGt = Rand_Tree<int, std::greater<int>>;
  using NodeGt = TreeGt::Node;
 
  TreeGt tree(42);
 
  std::vector<NodeGt *> nodes;
  for (int k : {1, 2, 3, 4, 5})
    {
      auto *p = new NodeGt(k);
      nodes.push_back(p);
      tree.insert(p);
    }
 
  EXPECT_EQ(tree.size(), 5u);
  EXPECT_TRUE(tree.verify());
 
  // With greater<int>, inorder should be descending
  std::vector<int> result;
  for (TreeGt::Iterator it(tree); it.has_curr(); it.next())
    result.push_back(KEY(it.get_curr()));
 
  EXPECT_EQ(result, (std::vector<int>{5, 4, 3, 2, 1}));
 
  // Clean up
  for (int k : {1, 2, 3, 4, 5})
    delete tree.remove(k);
}
 
// ============================================================================
// Edge Cases
// ============================================================================
 
TEST(RandTree, NegativeKeys)
{
  Tree tree(42);
  NodePool pool;
 
  for (int k : {-5, -3, -1, 0, 1, 3, 5})
    tree.insert(pool.make(k));
 
  EXPECT_EQ(tree.size(), 7u);
  EXPECT_TRUE(tree.verify());
 
  auto keys = inorder_keys<Node>(tree.getRoot());
  EXPECT_EQ(keys, (std::vector<int>{-5, -3, -1, 0, 1, 3, 5}));
 
  // Search negative keys
  EXPECT_NE(tree.search(-5), nullptr);
  EXPECT_NE(tree.search(-1), nullptr);
  EXPECT_EQ(tree.search(-2), nullptr);
}
 
TEST(RandTree, SingleElementOperations)
{
  Tree tree(42);
  NodePool pool;
 
  auto *p = pool.make(42);
  tree.insert(p);
 
  EXPECT_EQ(tree.size(), 1u);
  EXPECT_EQ(KEY(tree.select(0)), 42);
 
  auto [pos, node] = tree.position(42);
  EXPECT_EQ(pos, 0);
  EXPECT_EQ(KEY(node), 42);
 
  auto *removed = tree.remove(42);
  ASSERT_NE(removed, nullptr);
  pool.forget(removed);
  delete removed;
 
  EXPECT_EQ(tree.size(), 0u);
}
 
// ============================================================================
// Stress Tests
// ============================================================================
 
TEST(RandTree, RandomInsertSearchRemove)
{
  Tree tree(42);
  NodePool pool;
  std::set<int> oracle;
 
  std::mt19937 rng(12345);
  std::uniform_int_distribution<int> dist(0, 999);
 
  // Insert phase
  for (int i = 0; i < 500; ++i)
    {
      int k = dist(rng);
      if (oracle.count(k) == 0)
        {
          ASSERT_NE(tree.insert(pool.make(k)), nullptr);
          oracle.insert(k);
        }
    }
 
  EXPECT_EQ(tree.size(), oracle.size());
  EXPECT_TRUE(tree.verify());
 
  // Search phase
  for (int i = 0; i < 200; ++i)
    {
      int k = dist(rng);
      auto *found = tree.search(k);
      if (oracle.count(k))
        EXPECT_NE(found, nullptr);
      else
        EXPECT_EQ(found, nullptr);
    }
 
  // Remove phase
  for (int i = 0; i < 200; ++i)
    {
      int k = dist(rng);
      auto *removed = tree.remove(k);
      if (oracle.count(k))
        {
          ASSERT_NE(removed, nullptr);
          oracle.erase(k);
          pool.forget(removed);
          delete removed;
        }
      else
        {
          EXPECT_EQ(removed, nullptr);
        }
    }
 
  EXPECT_EQ(tree.size(), oracle.size());
  EXPECT_TRUE(tree.verify());
 
  // Verify remaining keys
  auto keys = inorder_keys<Node>(tree.getRoot());
  EXPECT_EQ(keys, std::vector<int>(oracle.begin(), oracle.end()));
}
 
TEST(RandTree, LargeTreeOperations)
{
  Tree tree(42);
  NodePool pool;
 
  const int N = 5000;
 
  // Insert N elements
  for (int k = 0; k < N; ++k)
    tree.insert(pool.make(k));
 
  EXPECT_EQ(tree.size(), static_cast<size_t>(N));
  EXPECT_TRUE(tree.verify());
 
  // Verify select works correctly
  for (int i = 0; i < 10; ++i)
    EXPECT_EQ(KEY(tree.select(i)), i);
 
  // Remove half
  for (int k = 0; k < N; k += 2)
    {
      auto *removed = tree.remove(k);
      ASSERT_NE(removed, nullptr);
      pool.forget(removed);
      delete removed;
    }
 
  EXPECT_EQ(tree.size(), static_cast<size_t>(N / 2));
  EXPECT_TRUE(tree.verify());
 
  // Verify remaining elements
  for (int k = 1; k < N; k += 2)
    EXPECT_NE(tree.search(k), nullptr);
}
 
// ============================================================================
// Rand_Tree_Vtl Tests
// ============================================================================
 
TEST(RandTreeVtl, BasicOperations)
{
  using TreeVtl = Rand_Tree_Vtl<int>;
  using NodeVtl = TreeVtl::Node;
 
  TreeVtl tree(42);
 
  for (int k : {1, 2, 3, 4, 5})
    tree.insert(new NodeVtl(k));
 
  EXPECT_EQ(tree.size(), 5u);
  EXPECT_TRUE(tree.verify());
 
  // Clean up properly using remove to avoid memory leaks
  for (int k : {1, 2, 3, 4, 5})
    delete tree.remove(k);
}
 
// ============================================================================
// Verify Method Tests
// ============================================================================
 
TEST(RandTree, VerifyDetectsValidTree)
{
  Tree tree(42);
  NodePool pool;
 
  EXPECT_TRUE(tree.verify()); // empty tree is valid
 
  for (int k : {5, 3, 7, 1, 4, 6, 8})
    tree.insert(pool.make(k));
 
  EXPECT_TRUE(tree.verify());
 
  // After various operations
  tree.remove(5);
  EXPECT_TRUE(tree.verify());
}
 
// ============================================================================
// API Coverage Tests
// ============================================================================
 
TEST(RandTree, GetRootReturnsReference)
{
  Tree tree(42);
  NodePool pool;
 
  Node *&root = tree.getRoot();
  EXPECT_EQ(root, Node::NullPtr);
 
  tree.insert(pool.make(10));
  EXPECT_NE(root, Node::NullPtr);
  EXPECT_EQ(KEY(root), 10);
}
 
TEST(RandTree, KeyCompAndGetCompare)
{
  Tree tree(42);
 
  auto &cmp1 = tree.key_comp();
  auto &cmp2 = tree.get_compare();
 
  // Both should return the same comparator
  EXPECT_TRUE(cmp1(1, 2));
  EXPECT_FALSE(cmp1(2, 1));
  EXPECT_TRUE(cmp2(1, 2));
  EXPECT_FALSE(cmp2(2, 1));
}
 
TEST(RandTree, GslRngObjectNotNull)
{
  Tree tree(42);
 
  auto *rng = tree.gsl_rng_object();
  EXPECT_NE(rng, nullptr);
}
 
TEST(RandTree, SetSeedChangesSequence)
{
  Tree tree1(42);
  Tree tree2(42);
  NodePool pool1, pool2;
 
  // Same seed, same insertion order -> same structure
  tree1.set_seed(999);
  tree2.set_seed(999);
 
  for (int k : {1, 2, 3, 4, 5})
    {
      tree1.insert(pool1.make(k));
      tree2.insert(pool2.make(k));
    }
 
  // Trees should have identical structure
  // (This is probabilistic but with same seed should be identical)
  EXPECT_EQ(tree1.size(), tree2.size());
}
 
// ============================================================================
// Copy Prevention Tests (compile-time)
// ============================================================================
 
static_assert(!std::is_copy_assignable_v<Tree>,
              "Rand_Tree should not be copy assignable");
 
static_assert(!std::is_copy_constructible_v<Tree>,
              "Rand_Tree should not be copy constructible");