Maximum Depth of Binary Tree (Easy)

Description

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.

Analysis

计算树的最大深度。。我第一感觉竟然是这么多的代码= =。明明几行就能解决，

My Solution

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//C++
/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
    int ans = 0;
    void dfs(TreeNode *root,int depth){
        if(root==NULL){
            if(depth>ans)
                ans = depth;
            return;
        }
        dfs(root->left,depth+1);
        dfs(root->right,depth+1);
    }
public:
    int maxDepth(TreeNode *root) {
        if(root==NULL)
            return 0;
        dfs(root,0);
        return ans;
    }
};