leetcode - Maximum Depth of Binary Tree

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.

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