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.
判断一棵树是否是高度平衡的二叉树，高度平衡的二叉树的定义是：二叉树的每个节点两个子树的深度差不超过1.
所以需要我们递归求出每个节点的左右子树的最大深度。然后比较判断。
/** * 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) { if (root == nullptr) return true; int left = depth(root->left); int right = depth(root->right); return abs(left - right) <= 1 && isBalanced(root->left) && isBalanced(root->right); } int depth(TreeNode* root) { if (root == nullptr) return 0; return max(depth(root->left), depth(root->right)) + 1; } }; // 9 ms
[LeetCode] Balanced Binary Tree
原文：http://www.cnblogs.com/immjc/p/7554702.html