Q257Rnd2.cpp

/**
 * 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;
    }
};