Leetcode 257. Binary Tree Paths

257. Binary Tree Paths

  • Total Accepted: 56430
  • Total Submissions: 185972
  • Difficulty: Easy

 

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"]

 

 

思路：DFS。遇到叶节点就push_back。注意c++中，to_string()可以直接将int转化为string类型。

 

 

代码：

形式一：

 1 class Solution {
 2 public:
 3     void binaryTreePaths(vector<string>& res,TreeNode* root,string str){
 4         if(!root) return;
 5         str=str+to_string(root->val);
 6         if(!root->left&&!root->right) res.push_back(str);
 7         binaryTreePaths(res,root->left,str+"->");
 8         binaryTreePaths(res,root->right,str+"->");
 9     }
10     vector<string> binaryTreePaths(TreeNode* root) {
11         vector<string> res;
12         binaryTreePaths(res,root,"");
13         return res;
14     }
15 };

 

形式二：

 1 class Solution {
 2 public:
 3     void binaryTreePaths(vector<string>& res,TreeNode* root,string str){
 4         if(!root->left&&!root->right) res.push_back(str);
 5         if(root->left) binaryTreePaths(res,root->left,str+"->"+to_string(root->left->val));
 6         if(root->right) binaryTreePaths(res,root->right,str+"->"+to_string(root->right->val));
 7     }
 8     vector<string> binaryTreePaths(TreeNode* root) {
 9         vector<string> res;
10         if(root) binaryTreePaths(res,root,to_string(root->val));
11         return res;
12     }
13 };

 

posted @ 2016-07-20 18:28  Deribs4  阅读(223)  评论(0)  编辑  收藏  举报