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[8/11] 98. Validate Binary Search Tree
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Medium
11369956Add to ListShareGiven the root
of a binary tree, determine if it is a valid binary search tree (BST).
A valid 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:
Input: root = [2,1,3] Output: true
Example 2:
Input: root = [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.
Constraints:
- The number of nodes in the tree is in the range
[1, 104]
. -231 <= Node.val <= 231 - 1
Accepted
1,560,125
Submissions
5,014,795
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학부유학생님의 댓글
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Runtime: 85 ms, faster than 24.13% of Python3 online submissions for Validate Binary Search Tree.
Memory Usage: 16.5 MB, less than 46.02% of Python3 online submissions for Validate Binary Search Tree.
Memory Usage: 16.5 MB, less than 46.02% of Python3 online submissions for Validate Binary Search Tree.
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def isValidBST(self, root: Optional[TreeNode], floor = float('-inf'), ceiling=float('inf')) -> bool:
return not root or (floor<root.val<ceiling and
self.isValidBST(root.left, floor, root.val) and
self.isValidBST(root.right, root.val, ceiling))
재민재민님의 댓글
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Runtime: 15 ms, faster than 77.39% of C++ online submissions for Validate Binary Search Tree.
Memory Usage: 21.8 MB, less than 30.99% of C++ online submissions for Validate Binary Search Tree.
Memory Usage: 21.8 MB, less than 30.99% of C++ online submissions for Validate Binary Search Tree.
class Solution {
public:
bool helper(TreeNode* root, long min, long max) {
if(!root)
return true;
if( min < root->val && root->val < max )
return helper(root->left, min, root->val) && helper(root->right, root->val, max);
else
return false;
}
bool isValidBST(TreeNode* root) {
return helper(root, LONG_MIN, LONG_MAX);
}
};