#include <iostream>
#include <string>
#include <algorithm>
using std::cout;
using std::endl;
using std::string;
int main()
{
string s = "abcd";
do {
cout << s << endl;
} while (next_permutation(s.begin(), s.end()));
cout << endl;
return 0;
}
/*
run:
abcd
abdc
acbd
acdb
adbc
adcb
bacd
badc
bcad
bcda
bdac
bdca
cabd
cadb
cbad
cbda
cdab
cdba
dabc
dacb
dbac
dbca
dcab
dcba
*/