LeetCode--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.

思路：递归。这道题很巧妙，通过计算左右子树的高度，判断高度差是否大于1来决定是不是平衡二叉树，所以问题就转换成求二叉树左右子树的高度的基本递归问题。

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    bool isBalanced(TreeNode* root) {        return balancedHeight(root)>=0;    }    int balancedHeight(TreeNode* root){        if(!root) return 0;        int left=balancedHeight(root->left);        int right=balancedHeight(root->right);        if(left<0||right<0||abs(left-right)>1) return -1;        return max(left,right)+1;    }};