c++非STL全排列

#include <cstdio>  
#include <vector>  
#include <string>  
#include <iostream>  
#include <algorithm>  
using namespace std;  
    
void permutation(vector<char> &res,string &str,vector<int> &used)  
{  
  if(res.size()==str.length())  
  {  
    for(int i=0;i<res.size();++i)  
      printf("%c",res[i]);  
    printf("
");  
    return;  
  }  
  for(int i=0;i<str.length();++i)  
  {  
    if(used[i] || (i!=0 && str[i]==str[i-1] && used[i-1]))  
      continue;  
    used[i]=1;  
    res.push_back(str[i]);  
    permutation(res,str,used);  
    used[i]=0;  
    res.pop_back();  
  }  
}  
    
int main()  
{  
  string strin;  
  while(cin>>strin)  
  {  
    vector<int> used(10,0);  
    sort(strin.begin(),strin.end());  
    vector<char> res;  
    permutation(res,strin,used);  
  }  
  return 0;  
}  
/**************************************************************
    Problem: 1369
    User: jasonhaven
    Language: C++
    Result: Accepted
    Time:500 ms
    Memory:1520 kb
****************************************************************/