leetcode 第110题 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：平衡二叉树满足左右子树深度之差不超过1。这里我们采用递归实现。

C++代码实现：

/**
* 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 depth(TreeNode *node){
if(node == NULL)
return 0;
return max(depth(node->left),depth(node->right))+1;
}

bool isBalanced(TreeNode* root) {
if(root == NULL)
return true;
if(abs(depth(root->left) - depth(root->right)) > 1)
return false;
return isBalanced(root->left) && isBalanced(root->right);
}
};