Sukat

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;

public class Main {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        String input = reader.readLine();
        int sum = 0;
        HashMap<Character, Integer> map = new HashMap<Character, Integer>();
        
        for (char c : input.toCharArray()) {
            int count = map.getOrDefault(c, 0) + 1;
            sum += count;
            map.put(c, count);
        }

        int lines = 0;
        StringBuilder out = new StringBuilder();

        for (char c : map.keySet().toArray(new Character[0])) {
            if (!map.containsKey(c)) continue;
            int selfCount = map.get(c);
            while (selfCount < sum) {
                char other = 'Ö'; // Ö=null
                for (char otherCandidate : map.keySet()) {
                    if (otherCandidate == c) continue;
                    else {
                        other = otherCandidate;
                        break;
                    }
                }
                
                if (other == 'Ö') break;

                lines++;
                out.append(c).append(other).append("\n");

                selfCount--;
                sum -= 2;
                int otherCount = map.get(other) - 1;

                if (otherCount > 0) {
                    map.put(other, otherCount);
                } else {
                    map.remove(other);
                }

                if (selfCount > 0) {
                    map.put(c, selfCount);
                } else {
                    map.remove(c);
                    break;
                }
            }
        }

        if (out.length() > 0) out.deleteCharAt(out.length() - 1);
        System.out.println(lines);
        System.out.println(out.toString());
    }
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 6

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 7

Group: 1, 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: WRONG ANSWER

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: WRONG ANSWER

Test 11

Group: 2, 3

Verdict: WRONG ANSWER

Test 12

Group: 2, 3

Verdict: WRONG ANSWER

Test 13

Group: 2, 3

Verdict: WRONG ANSWER

Test 14

Group: 2, 3

Verdict: WRONG ANSWER

Test 15

Group: 3

Verdict: WRONG ANSWER

Test 16

Group: 3

Verdict: ACCEPTED

Test 17

Group: 3

Verdict: WRONG ANSWER

Test 18

Group: 3

Verdict: ACCEPTED

Test 19

Group: 3

Verdict: WRONG ANSWER

Test 20

Group: 3

Verdict: WRONG ANSWER

Test 21

Group: 3

Verdict: WRONG ANSWER