#include <iostream>
#include <vector>
// In a permutation, the subset elements are listed in a specific order.
void create_2_letters_permutation(std::vector<char> letters) {
int size = letters.size();
for (int i = 0; i < size; i++) {
for (int j = 0; j < size; j++) {
if (i != j) { // Ensure different letters
std::cout << letters[i] << letters[j] << "\n";
}
}
}
}
int main() {
std::vector<char> letters = {'A', 'B', 'C', 'D'};
create_2_letters_permutation(letters);
}
/*
run:
AB
AC
AD
BA
BC
BD
CA
CB
CD
DA
DB
DC
*/