leetcode Binary Tree Paths

题目连接

https://leetcode.com/problems/binary-tree-paths/  

 Binary Tree Paths

Description

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:

$["1−>2−>5","1−>3"]$

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
	vector<string> binaryTreePaths(TreeNode* root) {
		ans.clear();
		if (!root) return ans;
		dfs(root, "");
		return ans;
	}
private:
	vector<string> ans;
	void dfs(TreeNode *x, string ret) {
		if (!x) return;
		if (!x->left && !x->right) {
			ans.push_back(ret + to_string(x->val));
			return;
		}
		dfs(x->left, ret + to_string(x->val) + "->");
		dfs(x->right, ret + to_string(x->val) + "->");
	}
};