257. Binary Tree Paths

#week18

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"]

分析：

这是一题比较简单的递归

通过递归来求解二叉树路径

题解：

 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>& result, TreeNode* root, string t) {
13         if (!root->left && !root->right) {
14             result.push_back(t);
15             return ;
16         }
17         
18         if (root->left) binaryTreePaths(result, root->left, t + "->" + to_string(root->left->val));
19         if (root->right) binaryTreePaths(result, root->right, t + "->" + to_string(root->right->val));
20         
21     }
22     vector<string> binaryTreePaths(TreeNode* root) {
23         vector<string> result;
24         if (!root) return result;
25         
26         binaryTreePaths(result, root, to_string(root->val));
27         return result;
28     }
29 };