using System;
using System.Collections.Generic;
public class Program
{
internal static ISet<string> generate_2_digit_permutations_from_3_digit_number(string threeDigitNumber) {
ISet<string> twoDigitPermutations = new HashSet<string>();
// Generate all two_digit_permutations of three_digit_number
for (int i = 0; i < threeDigitNumber.Length; i++) {
for (int j = 0; j < threeDigitNumber.Length; j++) {
if (i != j) {
twoDigitPermutations.Add("" + threeDigitNumber[i] + threeDigitNumber[j]);
}
}
}
return twoDigitPermutations;
}
public static void Main(string[] args)
{
string threeDigitNumber = "185";
ISet<string> twoDigitPermutations = generate_2_digit_permutations_from_3_digit_number(threeDigitNumber);
Console.WriteLine(string.Join(", ", twoDigitPermutations));
}
}
/*
run:
18, 15, 81, 85, 51, 58
*/
