110. 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(root == null)  //递归退出条件
           return true;
        int l = Depth(root.left);
        int r = Depth(root.right);
        if(Math.abs(l-r)>1)  //把不符合条件的部分 剪枝
          return false;
        
        return isBalanced(root.left)&&isBalanced(root.right);  
        
    }
    
    private int Depth(TreeNode root)
    {
        if(root == null)
          return 0;
        int Left = Depth(root.left);
        int Right = Depth(root.right);
        return (Left>Right)? (Left+1):(Right+1);
    }
}