tree-node.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_binNode.H>
# include <tpl_tree_node.H>
# include <ah-zip.H>
# include <ah-string-utils.H>
 
# include "tree-node-common.H"
 
using namespace std;
using namespace Aleph;
 
TEST(Tree_Node, on_isolated_node)
{
  Tree_Node<int> p;
 
  ASSERT_TRUE(p.is_root());
  ASSERT_TRUE(p.is_leaf());
  ASSERT_TRUE(p.is_leftmost());
  ASSERT_TRUE(p.is_rightmost());
  ASSERT_TRUE(p.get_child_list()->is_empty());
  ASSERT_TRUE(p.get_sibling_list()->is_empty());
 
  ASSERT_EQ(p.get_right_child(), nullptr);
  ASSERT_EQ(p.get_left_child(), nullptr);
 
  ASSERT_EQ(p.get_child(0), nullptr);
  ASSERT_EQ(p.get_parent(), nullptr);
 
  ASSERT_EQ(p.get_left_tree(), nullptr);
  ASSERT_EQ(p.get_right_tree(), nullptr);
 
  ASSERT_TRUE(p.children().is_empty());
 
  ASSERT_TRUE(p.traverse([] (auto) { return true; }));
  ASSERT_FALSE(p.traverse([] (auto) { return false; }));
 
  Tree_Node<int>::Iterator it = p.get_it();
  ASSERT_TRUE(it.has_curr());
  ASSERT_EQ(it.get_curr(), &p);
  ASSERT_NO_THROW(it.next());
  ASSERT_FALSE(it.has_curr());
  ASSERT_THROW(it.get_curr(), overflow_error);
  ASSERT_THROW(it.next(), overflow_error);
  it.reset_first();
  ASSERT_TRUE(it.has_curr());
  ASSERT_EQ(it.get_curr(), &p);
  ASSERT_NO_THROW(it.next());
  ASSERT_FALSE(it.has_curr());
  ASSERT_THROW(it.get_curr(), overflow_error);
  ASSERT_THROW(it.next(), overflow_error);
 
  Tree_Node<int>::Children_Iterator cit(p);
  ASSERT_FALSE(cit.has_curr());
  ASSERT_THROW(cit.get_curr(), overflow_error);
  ASSERT_THROW(cit.next(), overflow_error);
}
 
TEST(Tree_Node, get_parent_tracks_multi_level_tree)
{
  Tree_Node<int> root(0);
  Tree_Node<int> left(1);
  Tree_Node<int> right(2);
  Tree_Node<int> left_left(3);
  Tree_Node<int> left_right(4);
  Tree_Node<int> deep(5);
 
  root.insert_rightmost_child(&left);
  root.insert_rightmost_child(&right);
  left.insert_rightmost_child(&left_left);
  left.insert_rightmost_child(&left_right);
  left_left.insert_rightmost_child(&deep);
 
  ASSERT_EQ(root.get_parent(), nullptr);
  ASSERT_EQ(left.get_parent(), &root);
  ASSERT_EQ(right.get_parent(), &root);
  ASSERT_EQ(left_left.get_parent(), &left);
  ASSERT_EQ(left_right.get_parent(), &left);
  ASSERT_EQ(deep.get_parent(), &left_left);
}
 
TEST(Tree_Node, insert_leftmost_child_preserves_existing_subtree_parent_links)
{
  Tree_Node<int> root(0);
  Tree_Node<int> old_left(1);
  Tree_Node<int> old_right(2);
  Tree_Node<int> old_left_child(3);
  Tree_Node<int> new_left(4);
 
  root.insert_rightmost_child(&old_left);
  root.insert_rightmost_child(&old_right);
  old_left.insert_rightmost_child(&old_left_child);
 
  root.insert_leftmost_child(&new_left);
 
  ASSERT_EQ(root.get_left_child(), &new_left);
  ASSERT_EQ(root.get_child(0), &new_left);
  ASSERT_EQ(root.get_child(1), &old_left);
  ASSERT_EQ(root.get_child(2), &old_right);
 
  ASSERT_EQ(new_left.get_parent(), &root);
  ASSERT_EQ(old_left.get_parent(), &root);
  ASSERT_EQ(old_right.get_parent(), &root);
  ASSERT_EQ(old_left_child.get_parent(), &old_left);
 
  ASSERT_TRUE(new_left.is_leftmost());
  ASSERT_FALSE(new_left.is_rightmost());
  ASSERT_FALSE(old_left.is_leftmost());
  ASSERT_FALSE(old_right.is_leftmost());
  ASSERT_TRUE(old_right.is_rightmost());
}
 
TEST(Tree_Node, insert_left_sibling_before_leftmost_child_updates_spine)
{
  Tree_Node<int> root(0);
  Tree_Node<int> old_left(1);
  Tree_Node<int> right(2);
  Tree_Node<int> old_left_child(3);
  Tree_Node<int> new_left(4);
 
  root.insert_rightmost_child(&old_left);
  root.insert_rightmost_child(&right);
  old_left.insert_rightmost_child(&old_left_child);
 
  old_left.insert_left_sibling(&new_left);
 
  ASSERT_EQ(root.get_left_child(), &new_left);
  ASSERT_EQ(root.get_child(0), &new_left);
  ASSERT_EQ(root.get_child(1), &old_left);
  ASSERT_EQ(root.get_child(2), &right);
 
  ASSERT_EQ(new_left.get_parent(), &root);
  ASSERT_EQ(old_left.get_parent(), &root);
  ASSERT_EQ(right.get_parent(), &root);
  ASSERT_EQ(old_left_child.get_parent(), &old_left);
 
  ASSERT_TRUE(new_left.is_leftmost());
  ASSERT_FALSE(new_left.is_rightmost());
  ASSERT_FALSE(old_left.is_leftmost());
  ASSERT_FALSE(right.is_leftmost());
  ASSERT_TRUE(right.is_rightmost());
}
 
TEST(Tree_Node, bin_to_forest_preserves_each_forest_root_flag)
{
  BinNode<int> n1(1);
  BinNode<int> n2(2);
  BinNode<int> n3(3);
 
  RLINK(&n1) = &n2;
  RLINK(&n2) = &n3;
 
  auto * forest = bin_to_forest<Tree_Node<int>, BinNode<int>>(&n1);
  ASSERT_NE(forest, nullptr);
 
  size_t count = 0;
  for (auto * t = forest; t != nullptr; t = t->get_right_sibling(), ++count)
    {
      EXPECT_TRUE(t->is_root()) << "tree key " << t->get_key()
                                << " must remain a forest root";
      EXPECT_EQ(t->get_parent(), nullptr);
    }
 
  EXPECT_EQ(count, 3);
  destroy_forest(forest);
}
 
TEST(Tree_Node, insert_right_sibling_on_root_links_forest_roots)
{
  Tree_Node<int> tree1(1);
  Tree_Node<int> tree2(2);
  Tree_Node<int> tree3(3);
 
  tree1.insert_right_sibling(&tree2);
  tree2.insert_right_sibling(&tree3);
 
  ASSERT_EQ(tree1.get_right_tree(), &tree2);
  ASSERT_EQ(tree2.get_right_tree(), &tree3);
  ASSERT_EQ(tree3.get_right_tree(), nullptr);
 
  ASSERT_TRUE(tree1.is_root());
  ASSERT_TRUE(tree2.is_root());
  ASSERT_TRUE(tree3.is_root());
 
  ASSERT_EQ(tree1.get_parent(), nullptr);
  ASSERT_EQ(tree2.get_parent(), nullptr);
  ASSERT_EQ(tree3.get_parent(), nullptr);
}
 
TEST(Tree_Node, unique_sibling_macro_tracks_sibling_links)
{
  Tree_Node<int> isolated(0);
  ASSERT_TRUE(IS_UNIQUE_SIBLING(&isolated));
 
  Tree_Node<int> root(1);
  Tree_Node<int> only_child(2);
  root.insert_rightmost_child(&only_child);
  ASSERT_TRUE(IS_UNIQUE_SIBLING(&only_child));
 
  Tree_Node<int> other_child(3);
  root.insert_rightmost_child(&other_child);
  ASSERT_FALSE(IS_UNIQUE_SIBLING(&only_child));
  ASSERT_FALSE(IS_UNIQUE_SIBLING(&other_child));
 
  Tree_Node<int> tree1(4);
  Tree_Node<int> tree2(5);
  tree1.insert_tree_to_right(&tree2);
  ASSERT_FALSE(IS_UNIQUE_SIBLING(&tree1));
  ASSERT_FALSE(IS_UNIQUE_SIBLING(&tree2));
}
 
TEST(Tree_Node, destroy_tree_on_non_leftmost_child_regression)
{
  Tree_Node<int>* root = new Tree_Node<int>(1);
  Tree_Node<int>* child1 = new Tree_Node<int>(2);
  Tree_Node<int>* child2 = new Tree_Node<int>(3);
  
  root->insert_rightmost_child(child1);
  root->insert_rightmost_child(child2);
 
  // Layout: child1 -> child2 (rightmost)
  // Destroying a non-leftmost sibling with a left sibling
  destroy_tree(child2);
 
  ASSERT_EQ(root->get_left_child(), child1);
  ASSERT_EQ(root->get_right_child(), child1);
  ASSERT_TRUE(IS_UNIQUE_SIBLING(child1));
  ASSERT_TRUE(child1->is_rightmost());
  ASSERT_EQ(child1->get_right_sibling(), nullptr);
 
  destroy_tree(root);
}
 
TEST(Tree_Node, destroy_tree_restores_is_rightmost_on_surviving_sibling)
{
  // Regression: destroy_tree() unlinked a node from its sibling list
  // without restoring is_rightmost()/is_leftmost() on the neighbor taking
  // its place. get_right_child()/get_left_child() use the raw (flag-blind)
  // Dlink links and so cannot detect this; get_right_sibling() and anything
  // built on it (for_each_child(), Children_Iterator) are flag-gated and
  // did loop forever on the surviving sibling before this fix.
  auto *root = new Tree_Node<int>(0);
  auto *a = new Tree_Node<int>(1);
  auto *b = new Tree_Node<int>(2);
  auto *c = new Tree_Node<int>(3);
  root->insert_rightmost_child(a);
  root->insert_rightmost_child(b);
  root->insert_rightmost_child(c);  // root -> a, b, c (c is rightmost)
 
  destroy_tree(c);
 
  EXPECT_TRUE(b->is_rightmost());
  EXPECT_EQ(b->get_right_sibling(), nullptr);
 
  int count = 0;
  root->for_each_child([&count](auto) { ++count; });
  EXPECT_EQ(count, 2);  // a, b -- would loop forever before the fix
 
  destroy_tree(root);
}
 
TEST(Tree_Node, destroy_tree_restores_is_leftmost_on_surviving_sibling)
{
  // Symmetric case: destroying the current leftmost child must promote
  // its former right neighbor to is_leftmost().
  auto *root = new Tree_Node<int>(0);
  auto *a = new Tree_Node<int>(1);
  auto *b = new Tree_Node<int>(2);
  auto *c = new Tree_Node<int>(3);
  root->insert_rightmost_child(a);
  root->insert_rightmost_child(b);
  root->insert_rightmost_child(c);  // root -> a (leftmost), b, c
 
  destroy_tree(a);
 
  EXPECT_TRUE(b->is_leftmost());
  EXPECT_EQ(b->get_left_sibling(), nullptr);
  EXPECT_EQ(root->get_left_child(), b);
 
  int count = 0;
  root->for_each_child([&count](auto) { ++count; });
  EXPECT_EQ(count, 2);  // b, c
 
  destroy_tree(root);
}
 
TEST(Tree_Node, simple_tree_construction_and_destruction)
{
  Tree_Node<int> p1 = 1;
  Tree_Node<int> p2 = 2;
  Tree_Node<int> p3 = 3;
  Tree_Node<int> p4 = 4;
  Tree_Node<int> p5 = 5;
 
  /* 1  insert_leftmost_child() test
     |
     2
  */
  p1.insert_leftmost_child(&p2); 
  ASSERT_TRUE(p1.is_root());
  ASSERT_TRUE(p1.is_leftmost());
  ASSERT_TRUE(p1.is_rightmost());
  ASSERT_FALSE(p1.is_leaf());
  ASSERT_FALSE(p2.is_root());
  ASSERT_TRUE(p2.is_leftmost());
  ASSERT_TRUE(p2.is_rightmost());
 
  /*     1   insert_rightmost_child() test
  /\
       2 3
   */
  p1.insert_rightmost_child(&p3);
  ASSERT_TRUE(p1.is_root());
  ASSERT_TRUE(p1.is_leftmost());
  ASSERT_TRUE(p1.is_rightmost());
  ASSERT_FALSE(p1.is_leaf());
  ASSERT_TRUE(p2.is_leaf());
  ASSERT_FALSE(p2.is_root());
  ASSERT_TRUE(p2.is_leftmost());
  ASSERT_FALSE(p2.is_rightmost());
  ASSERT_TRUE(p2.is_leaf());
  ASSERT_FALSE(p3.is_root());
  ASSERT_FALSE(p3.is_leftmost());
  ASSERT_TRUE(p3.is_rightmost());
 
  /*        0
          / | \
         2  3 5
   */
  p3.insert_right_sibling(&p5);
  ASSERT_TRUE(p1.is_root());
  ASSERT_TRUE(p1.is_rightmost());
  ASSERT_TRUE(p1.is_leftmost());
  ASSERT_FALSE(p1.is_leaf());
  ASSERT_FALSE(p2.is_root());
  ASSERT_TRUE(p2.is_leftmost());
  ASSERT_FALSE(p2.is_rightmost());
  ASSERT_TRUE(p2.is_leaf());
  ASSERT_FALSE(p3.is_root());
  ASSERT_FALSE(p3.is_leftmost());
  ASSERT_FALSE(p3.is_rightmost());
  ASSERT_TRUE(p3.is_leaf());
  ASSERT_FALSE(p5.is_leftmost());
  ASSERT_TRUE(p5.is_rightmost());
  ASSERT_FALSE(p5.is_root());
  ASSERT_TRUE(p5.is_leaf());
 
  /*            1
           /  /  |  | 
     2 3   4  5
   */
  p5.insert_left_sibling(&p4);
  ASSERT_TRUE(p1.is_root());
  ASSERT_TRUE(p1.is_rightmost());
  ASSERT_TRUE(p1.is_leftmost());
  ASSERT_FALSE(p1.is_leaf());
  ASSERT_FALSE(p2.is_root());
  ASSERT_TRUE(p2.is_leftmost());
  ASSERT_FALSE(p2.is_rightmost());
  ASSERT_TRUE(p2.is_leaf());
 
  ASSERT_FALSE(p3.is_root());
  ASSERT_FALSE(p3.is_leftmost());
  ASSERT_FALSE(p3.is_rightmost());
  ASSERT_TRUE(p3.is_leaf());
 
  ASSERT_FALSE(p4.is_root());
  ASSERT_FALSE(p4.is_leftmost());
  ASSERT_FALSE(p4.is_rightmost());
  ASSERT_TRUE(p4.is_leaf());
 
  ASSERT_FALSE(p5.is_leftmost());
  ASSERT_TRUE(p5.is_rightmost());
  ASSERT_FALSE(p5.is_root());
  ASSERT_TRUE(p5.is_leaf());
 
  ASSERT_EQ(p1.get_left_child(), &p2);
  ASSERT_EQ(p1.get_right_child(), &p5);
 
  ASSERT_EQ(p2.get_left_sibling(), nullptr);
  ASSERT_EQ(p2.get_right_sibling(), &p3);
 
  ASSERT_EQ(p3.get_left_sibling(), &p2);
  ASSERT_EQ(p3.get_right_sibling(), &p4);
 
  ASSERT_EQ(p4.get_left_sibling(), &p3);
  ASSERT_EQ(p4.get_right_sibling(), &p5);
 
  ASSERT_EQ(p5.get_left_sibling(), &p4);
  ASSERT_EQ(p5.get_right_sibling(), nullptr);
 
  ASSERT_EQ(p1.get_child(0), &p2);
  ASSERT_EQ(p1.get_child(1), &p3);
  ASSERT_EQ(p1.get_child(2), &p4);
  ASSERT_EQ(p1.get_child(3), &p5);
 
  int k = 0;
  ASSERT_TRUE(p1.traverse([&k] (auto p) { return p->get_key() == ++k; }));
  ASSERT_EQ(k, 5);
  k = 1;
  ASSERT_TRUE(p1.children_nodes().traverse([&k] (auto p)
             { return p->get_key() == ++k; }));
  ASSERT_EQ(k, 5);
  k = 1;
  ASSERT_TRUE(p1.children().traverse([&k] (auto i) { return i == ++k; }));
  ASSERT_EQ(k, 5);
}
 
TEST(Tree_Node, Iterator_on_extreme_cases)
{
  {
    Tree_Node<int>::Iterator it = nullptr;
    ASSERT_FALSE(it.has_curr());
    ASSERT_THROW(it.get_curr(), overflow_error);
    ASSERT_THROW(it.next(), overflow_error);
  }
 
  {
    Tree_Node<int> p(0);
    auto it = p.get_it();
    ASSERT_TRUE(it.has_curr());
    ASSERT_EQ(it.get_pos(), 0);
    ASSERT_NO_THROW(it.next());
    ASSERT_FALSE(it.has_curr());
    ASSERT_EQ(it.get_pos(), 1);
    ASSERT_THROW(it.get_curr(), overflow_error);
    ASSERT_THROW(it.next(), overflow_error);
  }
 
  {
    Tree_Node<int> p0(0);
    Tree_Node<int> p1(1);
    p0.insert_leftmost_child(&p1);
    auto it = p0.get_it();
    ASSERT_TRUE(it.has_curr());
    ASSERT_EQ(it.get_curr(), &p0);
    ASSERT_NO_THROW(it.next());
    ASSERT_TRUE(it.has_curr());
    ASSERT_EQ(it.get_curr(), &p1);
    ASSERT_NO_THROW(it.next());
    ASSERT_FALSE(it.has_curr());
    ASSERT_THROW(it.get_curr(), overflow_error);
    ASSERT_THROW(it.next(), overflow_error);
 
    ASSERT_NO_THROW(it.reset_first());
    ASSERT_TRUE(it.has_curr());
    ASSERT_EQ(it.get_curr(), &p0);
    ASSERT_NO_THROW(it.next());
    ASSERT_TRUE(it.has_curr());
    ASSERT_EQ(it.get_curr(), &p1);
    ASSERT_NO_THROW(it.next());
    ASSERT_FALSE(it.has_curr());
    ASSERT_THROW(it.get_curr(), overflow_error);
    ASSERT_THROW(it.next(), overflow_error);
  }
}
 
TEST_F(Simple_Tree, Iterators)
{
  auto itl = l.get_it();
  size_t k = 0;
  for (auto it = root->get_it(); it.has_curr(); it.next(), itl.next(), ++k)
    ASSERT_EQ(it.get_curr()->get_key(), itl.get_curr());
  ASSERT_GT(k, 0);
}
 
TEST(Tree_Node, clone_on_extreme_cases)
{
  {
    Tree_Node<int> * root = nullptr;
    ASSERT_EQ(clone_tree(root), nullptr);
  }
  {
    Tree_Node<int> root(5);
    auto rootp = clone_tree(&root);
    ASSERT_NE(rootp, nullptr);
    ASSERT_EQ(root.get_key(), rootp->get_key());
    destroy_tree(rootp);
  }
}
 
TEST_F(Simple_Tree, level_traversal)
{
  int i = 0;
  ASSERT_TRUE(root->level_traverse([&i] (auto p)
             {
         return p->get_key() == i++;
             }));
  ASSERT_EQ(i, 31);
}
 
TEST_F(Simple_Tree, clone)
{
  Tree_Node<int> * clone = clone_tree(root);
  using It = Tree_Node<int>::Iterator;
  using Pit = Pair_Iterator<It>;
  for (Pit it{It(root), It(clone)}; it.has_curr(); it.next())
    {
      auto p = it.get_curr();
      ASSERT_EQ(p.first->get_key(), p.second->get_key());
    }
  destroy_tree(clone);
}
 
TEST(Tree_Node, traverse_on_extreme_cases)
{
  {
    Tree_Node<int> * root = nullptr;
    ASSERT_EQ(root, nullptr);
  }
  {
    Tree_Node<int> root(5);
    size_t k = 0;
    ASSERT_TRUE(root.traverse([&k] (auto p) { k++; return p->get_key() == 5; }));
    ASSERT_EQ(k, 1);
  }
}
 
TEST(Tree_Node, are_tree_equal_uses_custom_comparator_recursively)
{
  using Node = Tree_Node<std::string>;
 
  auto * t1 = new Node("root");
  t1->insert_rightmost_child(new Node("A"));
  t1->insert_rightmost_child(new Node("B"));
 
  auto * t2 = new Node("ROOT");
  t2->insert_rightmost_child(new Node("a"));
  t2->insert_rightmost_child(new Node("b"));
 
  auto nocase = [] (const std::string & a, const std::string & b)
  {
    if (a.size() != b.size())
      return false;
    for (size_t i = 0; i < a.size(); ++i)
      if (std::tolower(static_cast<unsigned char>(a[i])) !=
          std::tolower(static_cast<unsigned char>(b[i])))
        return false;
    return true;
  };
 
  ASSERT_TRUE((are_tree_equal<Node, decltype(nocase)>(t1, t2, nocase)));
 
  destroy_tree(t1);
  destroy_tree(t2);
}
 
TEST_F(Simple_Tree, traverse)
{
  auto it = l.get_it();
  size_t k = 0;
  auto ret = root->traverse([&it, &k] (auto p)
    {
      bool r = p->get_key() == it.get_curr();
      it.next(); ++k;
      return r;
    });
  ASSERT_TRUE(ret);
  ASSERT_EQ(k, l.size());
}
 
TEST_F(Simple_Tree, deway)
{
  int d[100];
  size_t sz;
  auto p = search_deway(root, 14, d, 100, sz);
  ASSERT_EQ(p->get_key(), 14);
  ASSERT_EQ(sz, 3);
  ASSERT_EQ(d[0], 0);
  ASSERT_EQ(d[1], 1);
  ASSERT_EQ(d[2], 3);
}
 
/*                                    0
 
      1              2                3                 4                    5
 
6 7 8 9 10     11 12 13 14 15  16 17 18 19 20     21 22 23 24 25 26   27 28 29 30 31
 
*/
 
TEST_F(Three_Trees, insertion_of_trees)
{
  auto t1 = clone_tree(root1); 
  auto t2 = clone_tree(root2);
  auto t3 = clone_tree(root3);
 
  t1->insert_tree_to_right(t3);
  t1->insert_tree_to_right(t2);
 
  DynList<Tree_Node<int>*> tlist = { t1, t2, t3 };
  DynList<Tree_Node<int>*> flist = t1->trees();
 
  zip_for_each([] (auto t) { ASSERT_EQ(get<0>(t), get<1>(t)); }, tlist, flist);
  
  destroy_forest(t1);
}
 
TEST_F(Three_Trees, join)
{
  auto t = clone_tree(root1);
  auto t2 = clone_tree(root2);
 
  t->join(t2);
 
  DynList<int> l = { 0, 1, 2, 3, 4, 5, 31, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
         16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
         30, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43 };
 
  DynList<int> order;
  t->level_traverse([&order] (auto p) { order.append(p->get_key()); return true; });
 
  ASSERT_TRUE(eq(l, order));
 
  destroy_forest(t);
}