LeetCode OJ - 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.

分析：简单题，两种经典的方法。

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {    int ret = 0;public:    int maxDepth(TreeNode *root) {        if(!root) return 0;        ret = DFS(root);        return ret;    }    int DFS(TreeNode *root) {        if(!root->left && !root->right) {            return 1;        }        int r = 0;        int l = 0;        if(root->left) {            r = DFS(root->left);        }        if(root->right) {            l = DFS(root->right);        }                return max(r, l) + 1;    }};

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {    int ret = 0;public:    int maxDepth(TreeNode *root) {        if(!root) return 0;        DFS(root, 0);        return ret;    }    void DFS(TreeNode *root, int item) {        item++;        if(!root->left && !root->right) {            ret = max(ret, item);            return ;        }        if(root->left) DFS(root->left, item);        if(root->right) DFS(root->right, item);    }};