LeetCode OJ：Binary Tree Paths（二叉树路径）

Given a binary tree, return all root-to-leaf paths.

For example, given the following binary tree:

  1
 /   2     3
   5

All root-to-leaf paths are:

["1->2->5", "1->3"]

简单的遍历查找路径问题，代码如下：

 1 /**
 2  * Definition for a binary tree node.
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     vector<string> binaryTreePaths(TreeNode* root) {
13         ret.clear();
14         string s = "";
15         if(root == NULL) return ret;
16         dfs(root, s);
17         for(int i = 0; i < ret.size(); ++i){
18             ret[i].erase(ret[i].begin(), ret[i].begin() + 2);
19         }
20         return ret;
21     }
22
23     void dfs(TreeNode * root, string s)
24     {
25         stringstream ss;
26         ss << "->" << root->val;
27         s += ss.str();
28         if(root->left == NULL && root->right == NULL){
29             ret.push_back(s);
30             return;
31         }
32         if(root->left){
33             dfs(root->left, s);
34         }
35         if(root->right){
36             dfs(root->right, s);
37         }
38     }
39 private:
40     vector<string> ret;
41 };