LeetCode--Balanced Binary Tree

递归

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isBalanced(TreeNode *root) {
        pair<bool,int> res = isOk(root);
        return res.first;
    }
    pair<bool,int> isOk(TreeNode *root){
        if(root == NULL){
            return make_pair(true,0);
        }
        pair<bool,int> left = isOk(root->left);
        pair<bool,int> right = isOk(root->right);
        bool balanced = left.first&&right.first;
        if(abs(left.second-right.second) > 1){
            balanced = false;
        }
        int height = max(left.second,right.second)+1;
        return make_pair(balanced,height);
    }
};