LeetCode 104 Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
##題名説明所与の二叉木に対して、その最大の深さを返す##解題構想深さ優先探索DFS、再帰の方法

/* C++ */
/**
 * 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 maxDepth(TreeNode* root) {
       
        return (root == NULL)? 0: max(maxDepth(root->left),maxDepth(root->right))+1;
         
        
    }
};