leetcode 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.

这个题目要求判断是否是平衡二叉树。

我们使用一个辅助函数getDeep来获取平衡二叉树当前节点的深度，有一个要求就是如果判断出当前节点下面已经不是平衡二叉树了，那么就返回-1

/** * 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:    int getDeep(TreeNode* root) //返回深度，并且判断是否满足平衡二叉树，不满足返回-1    {        if (!root)            return 0;        else if (!root->left && !root->right)            return 1;                int ldeep = getDeep(root->left);        int rdeep = getDeep(root->right);                if (ldeep == -1 || rdeep == -1 || abs(ldeep - rdeep) > 1)            return -1;                return max(ldeep, rdeep) + 1;    }        bool isBalanced(TreeNode* root)     {        if (getDeep(root) == -1)            return false;        return true;    }};