leetcode 110 Balanced Binary Tree
2022-06-14 13:01 jetwill 阅读(15) 评论(0) 编辑 收藏 举报Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as:
a binary tree in which the left and right subtrees of every node differ in height by no more than 1.
Example 1:
Input: root = [3,9,20,null,null,15,7]
Output: true
Example 2:
Input: root = [1,2,2,3,3,null,null,4,4]
Output: false
Example 3:
Input: root = []
Output: true
来源:力扣(LeetCode)
链接:https://leetcode.cn/problems/balanced-binary-tree
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public boolean isBalanced(TreeNode root) {
if(root == null){
return true;
}
return helper(root) != -1;
}
private int helper(TreeNode root){
if(root == null){
return 0;
}
int left = helper(root.left);
int right = helper(root.right);
if(left == -1 || right == -1 || Math.abs(left - right) > 1){
return -1;
}
return Math.max(left, right) + 1;
}
}