tpl_binNodeGenerators_test.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  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
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*/
 
#include <vector>
 
#include <gtest/gtest.h>
 
#include <tpl_binNode.H>
#include <tpl_binNodeGenerators.H>
#include <tpl_binNodeUtils.H>
 
using namespace Aleph;
 
namespace
{
// Owns every node allocated for a test tree and frees them on destruction.
struct NodePool
{
  std::vector<BinNode<int> *> allocated;
 
  BinNode<int> *make(int k)
  {
    auto *p = new BinNode<int>(k);
    allocated.push_back(p);
    return p;
  }
 
  ~NodePool()
  {
    for (BinNode<int> *p : allocated)
      delete p;
  }
};
 
// Builds the complete binary tree with root 4, children 2 and 6, and
// grandchildren 1, 3, 5, 7 (in that left-to-right order).
BinNode<int> *build_balanced(NodePool &pool)
{
  BinNode<int> *n1 = pool.make(1);
  BinNode<int> *n2 = pool.make(2);
  BinNode<int> *n3 = pool.make(3);
  BinNode<int> *n4 = pool.make(4);
  BinNode<int> *n5 = pool.make(5);
  BinNode<int> *n6 = pool.make(6);
  BinNode<int> *n7 = pool.make(7);
 
  n4->getL() = n2;
  n4->getR() = n6;
  n2->getL() = n1;
  n2->getR() = n3;
  n6->getL() = n5;
  n6->getR() = n7;
  return n4;
}
 
// Right-degenerate chain 1 -> 2 -> 3 -> ... -> n (every node's right child
// is the next one; no left children). Exercises O(n)-deep traversal state.
BinNode<int> *build_degenerate_chain(NodePool &pool, int n)
{
  BinNode<int> *root = pool.make(1);
  BinNode<int> *tail = root;
  for (int k = 2; k <= n; ++k)
    {
      BinNode<int> *next = pool.make(k);
      tail->getR() = next;
      tail = next;
    }
  return root;
}
 
template <class Node>
std::vector<int> eager_in_order(Node *root)
{
  std::vector<int> keys;
  for_each_in_order<Node>(root, [&](Node *p) { keys.push_back(KEY(p)); });
  return keys;
}
 
template <class Node>
std::vector<int> eager_pre_order(Node *root)
{
  std::vector<int> keys;
  for_each_preorder<Node>(root, [&](Node *p) { keys.push_back(KEY(p)); });
  return keys;
}
 
template <class Node>
std::vector<int> eager_post_order(Node *root)
{
  std::vector<int> keys;
  for_each_postorder<Node>(root, [&](Node *p) { keys.push_back(KEY(p)); });
  return keys;
}
 
template <class Node>
std::vector<int> lazy_in_order_keys(Node *root)
{
  std::vector<int> keys;
  for (Node *n : lazy_in_order(root))
    keys.push_back(KEY(n));
  return keys;
}
 
template <class Node>
std::vector<int> lazy_pre_order_keys(Node *root)
{
  std::vector<int> keys;
  for (Node *n : lazy_pre_order(root))
    keys.push_back(KEY(n));
  return keys;
}
 
template <class Node>
std::vector<int> lazy_post_order_keys(Node *root)
{
  std::vector<int> keys;
  for (Node *n : lazy_post_order(root))
    keys.push_back(KEY(n));
  return keys;
}
}  // namespace
 
TEST(BinNodeGenerators, EmptyTreeYieldsNothing)
{
  EXPECT_TRUE(lazy_in_order_keys<BinNode<int>>(BinNode<int>::NullPtr).empty());
  EXPECT_TRUE(lazy_pre_order_keys<BinNode<int>>(BinNode<int>::NullPtr).empty());
  EXPECT_TRUE(lazy_post_order_keys<BinNode<int>>(BinNode<int>::NullPtr).empty());
}
 
TEST(BinNodeGenerators, SingleNodeYieldsThatNode)
{
  NodePool pool;
  BinNode<int> *root = pool.make(42);
  EXPECT_EQ(lazy_in_order_keys(root), (std::vector<int>{42}));
  EXPECT_EQ(lazy_pre_order_keys(root), (std::vector<int>{42}));
  EXPECT_EQ(lazy_post_order_keys(root), (std::vector<int>{42}));
}
 
TEST(BinNodeGenerators, InOrderMatchesEagerTraversal)
{
  NodePool pool;
  BinNode<int> *root = build_balanced(pool);
  EXPECT_EQ(lazy_in_order_keys(root), eager_in_order(root));
  EXPECT_EQ(lazy_in_order_keys(root), (std::vector<int>{1, 2, 3, 4, 5, 6, 7}));
}
 
TEST(BinNodeGenerators, PreOrderMatchesEagerTraversal)
{
  NodePool pool;
  BinNode<int> *root = build_balanced(pool);
  EXPECT_EQ(lazy_pre_order_keys(root), eager_pre_order(root));
  EXPECT_EQ(lazy_pre_order_keys(root), (std::vector<int>{4, 2, 1, 3, 6, 5, 7}));
}
 
TEST(BinNodeGenerators, PostOrderMatchesEagerTraversal)
{
  NodePool pool;
  BinNode<int> *root = build_balanced(pool);
  EXPECT_EQ(lazy_post_order_keys(root), eager_post_order(root));
  EXPECT_EQ(lazy_post_order_keys(root), (std::vector<int>{1, 3, 2, 5, 7, 6, 4}));
}
 
TEST(BinNodeGenerators, EarlyBreakStopsTraversal)
{
  NodePool pool;
  BinNode<int> *root = build_balanced(pool);
 
  std::vector<int> seen;
  for (BinNode<int> *n : lazy_in_order(root))
    {
      seen.push_back(KEY(n));
      if (KEY(n) == 3)
        break;
    }
  // In-order of the balanced tree starts 1, 2, 3, ...; must stop right there.
  EXPECT_EQ(seen, (std::vector<int>{1, 2, 3}));
}
 
TEST(BinNodeGenerators, DegenerateChainMatchesEagerTraversal)
{
  constexpr int n = 500;  // deep enough to exercise explicit stack state
  NodePool pool;
  BinNode<int> *root = build_degenerate_chain(pool, n);
 
  std::vector<int> expected(n);
  for (int i = 0; i < n; ++i)
    expected[i] = i + 1;
 
  // A right-only chain is its own pre-order, in-order and post-order... in
  // different shapes: in-order and pre-order both visit root-then-right
  // recursively so they coincide with the chain order; post-order visits
  // right subtree fully before the (chain) root, i.e. reverse order.
  EXPECT_EQ(lazy_in_order_keys(root), expected);
  EXPECT_EQ(lazy_pre_order_keys(root), expected);
  EXPECT_EQ(lazy_in_order_keys(root), eager_in_order(root));
  EXPECT_EQ(lazy_pre_order_keys(root), eager_pre_order(root));
  EXPECT_EQ(lazy_post_order_keys(root), eager_post_order(root));
 
  std::vector<int> reversed(expected.rbegin(), expected.rend());
  EXPECT_EQ(lazy_post_order_keys(root), reversed);
}