Leetcode-Validate BST 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 keysless thanthe node's key. The right subtree of a node contains only nodes with keysgreater thanth...
因为中序遍历是DFS的一种,Time complexity: O(N), space complexity: O(logN) publicclassSolution {intlastCheck =Integer.MIN_VALUE;publicbooleanisValidBST(TreeNode root){if(root ==null)returntrue;if(!isValidBST(root.left)){returnfalse; }if(lastCheck >= root.val){//only 'Less than' is v...
[leetcode] 98. Validate Binary Search Tree Description 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 contai...
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...
# 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]) -> bool: return Solution.dfs(root, None, Non...
# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = None # 方法一 class Solution(object): def isValidBST(self, root): """ :type root: TreeNode :rtype: bool """ res = [] self.in...
然后,若pre.val,也就是root.left.val,大于等于root.val的话,不满足BST定义,也返回false; 否则,继续执行pre = root,(现在去判断root.right,所以用root.val和root.right.val比较。)不满足就返回false. 如果跑完了右子树的DFS,还没有返回false,返回true. ...
判断一个树是否是 BST,按照定义递归判断即可 代码# Go package leetcode import "math" /** * Definition for a binary tree node. * type TreeNode struct { * Val int * Left *TreeNode * Right *TreeNode * } */ // 解法一,直接按照定义比较大小,比 root 节点小的都在左边,比 root 节点大的都...
[LeetCode]98.Validate Binary Search Tree 【题目】 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 keysless thanthe node's key....
LeetCode:Validate Binary Search Tree(验证二叉搜索树) 题目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......