如题，下列的程序是练习next_permutation用的，
#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<<"The 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;
}
输入rfs,结果为
对于frs是递增的我理解，但是后面的并不是呀，比如rfs？
