Leetcode 110

/**
 * 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) {
        int flag = 1;
        depth(root,0,flag);
        if(flag) return true;
        else return false;
    }
    
    int depth(TreeNode* root,int cnt,int& flag){
        if(root == NULL) return cnt;
        int a = depth(root->left,cnt+1,flag);
        int b = depth(root->right,cnt+1,flag);
        if(abs(a-b) > 1) flag = 0;
        return max(a,b);
    }
};

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