# Validate Binary Search Tree Problem & Solution

## C++ Solution

``````#pragma GCC optimize("Ofast,max-inline-insns-recursive")
#pragma GCC target("avx,avx2,fma")

static const int _=[]{ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();

/**
* struct TreeNode {
*   int val;
*   TreeNode *left;
*   TreeNode *right;
*   TreeNode() : val(0), left(nullptr), right(nullptr) {}
*   TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
*   TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
bool isValidBST(TreeNode* root) {
bool ok = true;
help(root, ok);

return ok;
}

private:
pair<long, long> help(TreeNode* root, bool& ok) {
if (root == nullptr || !ok) {
return {numeric_limits<long>::max(), numeric_limits<long>::min()};
}

if (root->left == nullptr && root->right == nullptr) {
return {root->val, root->val};
}

auto left = help(root->left, ok);
auto right = help(root->right, ok);

ok &= left.second < root->val && right.first > root->val;

return {min((long)root->val, min(left.first, right.first)),
max((long)root->val, max(left.second, right.second))};
}
};
``````

## Start Here

Many paths, there are. Follow yours, you must.