题目：给定一个二叉树,确定它是高度平衡的。对于这个问题,一棵高度平衡的二叉树的定义是：一棵二叉树中每个节点的两个子树的深度相差不会超过1。 

 样例

给出二叉树 A={3,9,20,#,#,15,7}, B={3,#,20,15,7}

A)  3            B)    3 
   / \                  \
  9  20                 20
    /  \                / \
   15   7              15  7

二叉树A是高度平衡的二叉树，但是B不是

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */


class Solution {
public:
    /*
     * @param root: The root of binary tree.
     * @return: True if this Binary tree is Balanced, or false.
     */
    bool isBalanced(TreeNode * root) {
        // write your code here
        return subTreeBalanced(root)!=-1;
    }
    int subTreeBalanced(TreeNode* node)
    {
        if(node==NULL)
            return 0;
        int left=subTreeBalanced(node->left);
        int right=subTreeBalanced(node->right);
        if(left==-1||right==-1||abs(left-right)>1)
        {
            return -1;
        }else
        {
            return max(left,right)+1;
        }
    }
};