257. 二叉树的所有路径C++

题目描述：给定一个二叉树，返回所有从根节点到叶子节点的路径。

解题思路：分别递归左子树和右子树。

代码：

/**
 * 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>res;
        if(root==nullptr) return res;

        binaryTreePaths(root,res,"");
        return res;
    }
    void binaryTreePaths(TreeNode*root,vector<string>&res,string path){
        path+=to_string(root->val);

        if(root->left==nullptr&&root->right==nullptr){
            res.push_back(path);
            return;
        }
        if(root->left) binaryTreePaths(root->left,res,path+"->");
        if(root->right) binaryTreePaths(root->right,res,path+"->");
    }
};