LeetCode Q257: Binary Tree Paths

Total Accepted: 44011 Total Submissions: 155436 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"]

Solution:

	/**
	* 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:
	void helper(TreeNode* root, vector<string>& res, string curStr){
	if(!root)
	return;
	if(!root->left&&!root->right){
	curStr=curStr+string("->")+to_string(root->val);
	res.push_back(curStr);
	return;
	}
	curStr=curStr+string("->")+to_string(root->val);
	helper(root->left, res, curStr);
	helper(root->right, res, curStr);
	}
	vector<string> binaryTreePaths(TreeNode* root) {
	vector<string> res;
	string curStr;
	if(!root)
	return res;
	curStr=to_string(root->val);
	if(!root->left&&!root->right){
	res.push_back(curStr);
	return res;
	}
	helper(root->left, res, curStr);
	helper(root->right, res, curStr);
	}
	};

view raw Q257BinaryTreePath.cpp hosted with ❤ by GitHub

Round 2 solution:

	/**
	* 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:
	void helper(vector<string>& res, string tmpRes, TreeNode* root){
	if(root==NULL)
	return;
	tmpRes = tmpRes.length()==0? to_string(root->val):tmpRes+string("->")+to_string(root->val);
	if(root->left==NULL&&root->right==NULL){
	res.push_back(tmpRes);
	return;
	}
	helper(res, tmpRes, root->left);
	helper(res, tmpRes, root->right);
	}
	vector<string> binaryTreePaths(TreeNode* root) {
	vector<string> res;
	string tmpRes;
	helper(res, tmpRes, root);
	return res;
	}
	};

view raw Q257Rnd2.cpp hosted with ❤ by GitHub