STL中简单算法实例sort()、next_permutation()

#include<iostream>
#include<string>
#include<algorithm>

using namespace std;

int main()
{
string letters;
cout<<"Enter the letters grouping (quit to quit): ";
while(cin>>letters && letters != "quit")
{
cout<<"Permutations of "<<letters<<endl;
sort(letters.begin(),letters.end());
cout<<letters<<endl;
while(next_permutation(letters.begin(),letters.end()))
cout<<letters<<endl;
cout<<"Enter next sequence (quit to quit):";
}

cout<<"Done.\n";
return 0;
}

Enter the letters grouping (quit to quit): abc
Permutations of abc
abc
acb
bac
bca
cab
cba
Enter next sequence (quit to quit):