leetcode 257. Binary Tree Paths

自己写的一个代码，注意这里判断是否是根节点前，应该把当前节点的value值push_back到res中

/**
 * 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<int> res;
        vector<vector<int>> result;
        binary(root,res,result);
        vector<string> str;
        for(int i = 0;i < result.size();i++){
            string tmp;
            for(int j = 0;j < result[i].size();j++){
                tmp += to_string(result[i][j]);
                tmp += "->";
            }
            str.push_back(tmp.substr(0,tmp.size() - 2));
        }
        return str;
    }
    void binary(TreeNode* root,vector<int> res,vector<vector<int>>& result){
        if(!root)
            return;
        res.push_back(root->val);
        if(!root->left && !root->right){
            result.push_back(res);
            return;
        }
        binary(root->left,res,result);
        binary(root->right,res,result);
    }
};