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.
Example 1:
2
/ \
1 3
Input: [2,1,3]
Output: true
Example 2:
5
/ \
1 4
/ \
3 6
Input: [5,1,4,null,null,3,6]
Output: false
Explanation: The root node's value is 5 but its right child's value is 4.
class Solution {
public boolean isValid(TreeNode root, long min, long max) {
if (root == null)
return true;
if (root.val >= min && root.val <= max) {
return isValid(root.left, min, (long) root.val - 1) && isValid(root.right, (long) root.val + 1, max);
}
return false;
}
public boolean isValidBST(TreeNode root) {
return isValid(root, Integer.MIN_VALUE, Integer.MAX_VALUE);
}
}
Last updated