I have checked it for many time, still have no ideas. Please help!

```
int maxDepth(struct TreeNode* root) {
if (root==NULL){
return 0;
}else{
int max_l = maxDepth(root->left);
int max_r = maxDepth(root->right);
return (max_l > max_r)? (1 + max_l) : (1 + max_r);
}
}
```

The run result:

2 / 38 test cases passed.

Status: Wrong Answer

Submitted: 27 minutes ago

Input:

[1,2]

Output:

1

Expected:

2