/**
 * 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:
    //找出最大和最小的深度,然后作差;
    int m = 0, n = 1000;
    void dfs(TreeNode *root, int d){
        if(!root){
            if(m < d) m= d;
            if(n > d) n = d;
            return ;
        }
        dfs(root->left, d + 1);
        dfs(root->right, d + 1);
    }
    bool isBalanced(TreeNode* root) {
        int d = 0;
        dfs(root, d);
        if(m - n <= 1) return true;
        return false;
    }
};