LeetCode（257）Binary Tree Paths

【题目】

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"]

【解答】

最直接的方法就是 DFS

【答案】

/** * 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(TreeNode* root,string temp,vector<string> &v)    {        string s;    s=to_string(root->val);        if (temp=="")    {    temp=s;    }    else    temp=temp+"->"+s;        if (root->left==NULL && root->right==NULL)    {    v.push_back(temp);    }    else    {        if (root->left)    {        dfs(root->left,temp,v);    }    if (root->right)        dfs(root->right,temp,v);    }    }    vector<string> binaryTreePaths(TreeNode* root)    {        vector<string> v;        if (root==NULL) //空树    return v;        string temp="";    dfs(root, temp, v);    return v;    }};