AcWing 71. 二叉树的深度（C++）- 树的遍历、递归

题目链接：https://www.acwing.com/problem/content/67/
题目如下：

class Solution {
public:
    int treeDepth(TreeNode* root) {
        return dfs(root);
    }
    int dfs(TreeNode* root){
        if(!root) return 0;
        
        int leftdep=dfs(root->left);
        int rightdep=dfs(root->right);
        
        return max(leftdep,rightdep)+1;
    }
};