104. Maximum Depth of Binary Tree

题目：Maximum Depth of Binary Tree

原题链接
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.
找出二叉树的最大深度

找深度的话只能不断的遍历下去了，深度优先和广度优先遍历都是可以的，这里就给出深度优先的代码：

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