Given a binary tree, determine if it is height-balanced.
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
Constraints:
[0, 5000].-104 <= Node.val <= 104/**
* 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) {
return solve(root) != -1;
}
int solve(TreeNode node) {
if (node == null)
return 0;
int lt = solve(node.left);
if (lt == -1)
return -1;
int rt = solve(node.right);
if (rt == -1)
return -1;
if (Math.abs(lt - rt) > 1)
return -1;
return Math.max(lt, rt) + 1;
}
}