leetcode 104_maximumdepthofbinarytree

 * 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 (TreeNode* root) {
        if(!root){
            return 0;
        }
        int left_an = maxDepth(root->left);
        int right_an = maxDepth(root->right);
        return (left_an>right_an)?(left_an+1):(right_an+1);
    }
};

class Solution {
public:
    int (TreeNode* root) {
        return root == NULL ? 0 : max(maxDepth(root -> left), maxDepth(root -> right)) + 1;
    }
};