Validate Binary Search Tree
Given a binary tree, determine if it is a valid binary search tree (BST).
Assume a BST is defined as follows:
- The left subtree of a node contains only nodes with keys less than the node's key.
- The right subtree of a node contains only nodes with keys greater than the node's key.
- Both the left and right subtrees must also be binary search trees.
confused what "{1,#,2,3}"
means? > read more on how binary tree is serialized on OJ.
class Solution { public: bool isValidBST(TreeNode *root) { return check(root, -(1<<30), 1<<30); } bool check(TreeNode* cur, int min_num ,int max_num) { if (cur == NULL) return true; if (cur->val > min_num && cur->val < max_num && check(cur->left, min_num, cur->val) && check(cur->right, cur->val, max_num)) return true; else return false; } };