LeetCode 257 二叉树所有路径

/**
 * 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>res;
    vector<string> binaryTreePaths(TreeNode* root) {
            string path="";
            dfs(root,path);
            return res;
    }
    void dfs(TreeNode* root,string path){
        if(!root){//防止整个树为空或者 非叶子节点只有一个子树的情况
            return;
        }
        if(!root->left&&!root->right){
            path+=to_string(root->val);
            res.push_back(path);
            return ;
        }   
        path+=to_string(root->val);
        path+="->";

        dfs(root->left,path);
        dfs(root->right,path);
    }
};