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 binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isBalanced(TreeNode root) {
        if(root==null){
            return true;
        }else if(isBalanced(root.left)&&isBalanced(root.right)){
            if(Math.abs(nodeHeight(root.left)-nodeHeight(root.right))>1){
                  return false;
             }
             return true;      
        }
         return false;   
    }
    
    int nodeHeight(TreeNode root){
        if(root==null){
            return 0;
        }else{
            int leftHeight;
            int rightHeight;
            leftHeight=nodeHeight(root.left);
            rightHeight=nodeHeight(root.right);
            return Math.max(leftHeight,rightHeight)+1;
        }    
    }
}

1 use recursive;

2 should consider 2 cases:

1) itself is balanced;

2) its left and right subtree is balanced;