Balanced Binary Tree

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) {
    	if (solve(root) == -1) {
    		return false;
    	}
    	return true;
    }

	private int solve(TreeNode root) {
		if (root == null) {
			return 0;
		}
		int left = solve(root.left);
		if (left == -1) {
			return -1;
		}
		int right = solve(root.right);
		if (right == -1) {
			return -1;
		}
		if (Math.abs(left-right) > 1) {
			return -1;
		} else {
			return Math.max(left, right)+1;
		}
	}
}