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.

/**
 * 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 cntHeight(TreeNode *root) {  
    if(root == NULL) return 0;  
    int left = cntHeight(root->left);  
    int right = cntHeight(root->right);  
    if(left < 0 || right < 0 || abs(left-right) > 1) return -1; //自定义 return -1，表示不平衡的情况  
    else  return max(left, right) + 1;  
} 

	bool isBalanced(TreeNode* root) {
		if (root == NULL)
			return true;

		int left = cntHeight(root->left);
		int right = cntHeight(root->right);

		if(left < 0 || right < 0 || abs(left-right) > 1) return false;  
        else return true;  


	}
};