[LeetCode]110. Balanced Binary Tree

Description:

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.

———————————————————————————————————————————————————

Solution:

题意：判断一个给定二叉树是否高度平衡（左右子树高度差不超过1）.

思路：递归。

/** * 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 getHeight(root) != -1;    }    int getHeight(TreeNode* r) {        if (r == NULL)            return 0;                int leftHeight = getHeight(r->left);        if (leftHeight == -1)            return -1;                int rightHeight = getHeight(r->right);        if (rightHeight == -1)                return -1;                if (abs(leftHeight - rightHeight) > 1)            return -1;                return 1 + max(leftHeight, rightHeight);    }};