Leetcode 257. Binary Tree Paths

Given a binary tree, return all root-to-leaf paths.

For example, given the following binary tree:

   1 /   \2     3 \  5

All root-to-leaf paths are:

["1->2->5", "1->3"]

求二叉树所有从根到叶的路径。

简单DFS

/** * 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 dfs(vector<string> &res, TreeNode* root, string now)    {        now += to_string(root->val);        if(root->left || root->right)        {            now += "->";            if(root->left) dfs(res, root->left, now);            if(root->right) dfs(res, root->right, now);        }        else            res.push_back(now);    }    vector<string> binaryTreePaths(TreeNode* root) {        vector<string> res;        if(!root) return res;        dfs(res, root, "");        return res;    }};