CheckTreeProperty

#include <cassert>
#include <iostream>
#include <ios>

template <typename T>
struct TreeNode {
    T value;
    TreeNode* left = nullptr;
    TreeNode* right = nullptr;
};

template <typename T>
void DeleteTree(TreeNode<T>* node) {
    if (!node) {
        return;
    }
    DeleteTree(node->left);
    DeleteTree(node->right);
    delete node;
}

template <typename T>
bool CheckTreeProperty(TreeNode<T>* node, const T* min, const T* max) {

    if (node == nullptr) {
        return true;
    }

    if (min != nullptr && node->value <= *min) {
        return false;
    }

    if (max != nullptr && node->value >= *max) {
        return false;
    }

    return CheckTreeProperty(node->left, min, &node->value) && CheckTreeProperty(node->right, &node->value, max);
}



template <typename T>
bool CheckTreeProperty(TreeNode<T>* node) {

    T* min = nullptr;
    T* max = nullptr;

    return  CheckTreeProperty(node, min, max);
}

int main() {

    using T = TreeNode<int>;
    T* root1 = new T{ 6, new T{4, new T{3}, new T{5}}, new T{7} };

    assert(CheckTreeProperty(root1));

    T* root2 = new T{ 6,
        new T{4, new T{3}, new T{5}}, new T{7, new T{8}} };

    assert(!CheckTreeProperty(root2));

    DeleteTree(root1);
    DeleteTree(root2);

    T* root3 = new T{ 4, new T{2}, new T{5, new T{1}, new T{7}} };

    std::cerr << std::boolalpha << CheckTreeProperty(root3) << std::endl;
    std::cerr << "OK" << std::endl;

    return 0;
}