Tree - Validate Binary Search Tree
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2023-12-01
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.
这题需要判断是不是一个正确的二叉搜索树,比较简单地一道题。
我们通过递归整棵树来解决,代码如下:
class Solution {
public:
bool isValidBST(TreeNode *root) {
return valid(root, numeric_limits<int>::min(), numeric_limits<int>::max());
}
bool valid(TreeNode* node, int minVal, int maxVal) {
if(!node) {
return true;
}
if(node->val <= minVal || node->val >= maxVal) {
return false;
}
return valid(node->left, minVal, node->val) &&
valid(node->right, node->val, maxVal);
}
};