257. Binary Tree Paths

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

For example, given the following binary tree:

All root-to-leaf paths are:

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

输出所有根节点到叶子节点的路径

C++(6ms):

 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     void binaryTreePaths(vector<string>& res ,TreeNode* root , string t) {
13         if (!root->left && !root->right){
14             res.push_back(t) ;
15             return ;
16         }
17         if (root->left) binaryTreePaths(res,root->left,t + "->" + to_string(root->left->val)) ;
18         if (root->right) binaryTreePaths(res,root->right,t + "->" + to_string(root->right->val)) ;
19     }
20         
21     vector<string> binaryTreePaths(TreeNode* root) {
22         vector<string> res ;
23         if (!root)
24             return res ;
25         binaryTreePaths(res,root,to_string(root->val)) ;
26         return res ;
27     }
28 };