leetcode || 104、Maximum Depth of Binary Tree

problem：

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.

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 Tree Depth-first Search

题意：输出二叉树的深度

thinking：

深度优先搜索，记录最大深度

code：

/** * Definition for binary tree * 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;        int max_dep=0;        dfs(0,max_dep,root);        return max_dep;    }protected:    void dfs(int dep,int &max_dep,TreeNode *node)    {        if(node==NULL)            return;        dep++;        max_dep = max(max_dep,dep);        if(node->left!=NULL)            dfs(dep,max_dep,node->left);        if(node->right!=NULL)            dfs(dep,max_dep,node->right);    }};