Sukat

#include <bits/stdc++.h>

#define forn(i, n) for (int i = 0; i<n; i++)
#define FOR(i, k, n) for (int i = k; i < n; i++)
#define N 1<<17
#define pb push_back
typedef long long ll;
using namespace std;

int n, a[30]; 
string s;
vector<pair<char, char>> v;

int main() {
    cin >> s;
    n = s.size();

    forn(i, n) {
        a[s[i]-'A']++;
    }

    forn(i, 30) {
        if (a[i] <= 0) continue;
        FOR(j, i+1, 30) {
            if (a[j] <= 0) continue;
            v.pb({(i+'A'), (j+'A')});
            a[i]--; a[j]--;
            if (a[i] <= 0) break;
            j--;
        }
    }

    cout << v.size() << "\n";
    forn(i, (int)v.size()) {
        cout << v[i].first << v[i].second;
        if (i != (int)v.size()-1) cout << endl; 
    }

}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

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