二叉树和分治法-Leetcode-104

题目链接：

https://leetcode.com/problems/maximum-depth-of-binary-tree/description/

/**
 * 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:
    //1. input and root , add 1 to  the depth ,untill ,it reach the leaf 
    int maxDepth(TreeNode* root) {
    
    return   root == NULL ? 0:max(maxDepth(root->left),maxDepth(root->right)) +1 ;
    }
};