lc110.java

// 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 depth of the two subtrees of every node never differ by more than 1.
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isBalanced(TreeNode root) {
      return depth(root) != -1;
    }
    private int depth(TreeNode root){
      if (root == null) return 0;
      if (root.left == null && root.right == null) return 1;
      int left = depth(root.left);
      int right = depth(root.right);
      if (left == -1 || right == -1 || Math.abs(left - right) > 1) return -1;
      else return Math.max(left, right);
    }
}