unix简化路径

Given an absolute path for a file (Unix-style), simplify it. 
For example, 
path = “/home/”, => “/home” 
path = “/a/./b/../../c/”, => “/c” 
click to show corner cases.

#include <iostream>
#include <vector>
#include <sstream>
using namespace std;
class Solution 
{
public:
    string simplifyPath(string path) 
    {
        string res;
        string tmp;
        vector<string> vec;
        stringstream ss(path);
        while(getline(ss,tmp,'/'))
        {
            if(tmp == "" or tmp == ".") 
                continue;
            if(tmp == ".." and !vec.empty())
            {
                vec.pop_back();
            }
            else if(tmp != "..")
            {
                vec.push_back(tmp);
            }
        }
        for(string str:vec)
        {
            res += "/" + str;
        }
        return res.empty()?"/":res;
    }
};

int main()
{
    string str;
    cin>>str;
    Solution s;
    cout<<s.simplifyPath(str)<<endl;
    return 0;
    
}