Leetcode 257. Binary Tree Paths

/**
 * 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) {
        vector<string> v;
        getPath(true, v, root, "");
        return v;
    }
    void getPath(bool start, vector<string>& v, TreeNode* root, string str) {
        if(!root) return;
        if(!start) str += "->"; 
        str += to_string(root->val);
        if(!root->left && !root->right) v.push_back(str);
        getPath(false, v, root->left, str);
        getPath(false, v, root->right, str);
    }
};