Sukat

#include <bits/stdc++.h>
using namespace std;
typedef int64_t ll;
const int Q = 1e9+7;
const int O = 1e6;

vector<pair<char,char>> V;
pair<int,char> B[30];
string S;

int main() {
    cin >> S;
    for (int i=0; i < 26; ++i) B[i].second = 'A'+i;
    for (char c : S) {
        int i = (int)c-'A';
        ++B[i].first;
    }
    while (true) {
        int a0=-1, b0=-1;
        int a = 0, b = 0;
        for (int i=0; i < 26; ++i) {
            if (B[i].first > a) {
                b = a;
                b0 = a0;
                a = B[i].first;
                a0 = i;
            } else if (B[i].first > b) {
                b = B[i].first;
                b0 = i;
            }
        }
        if (b0 == -1) {
            break;
        }
        --B[a0].first; --B[b0].first;
        V.push_back({B[a0].second,B[b0].second});
    }
    cout << V.size() << '\n';
    for (auto [a,b] : V) {
        cout << a << b << '\n';
    }
}

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: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: ACCEPTED

Test 7

Group: 1, 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: ACCEPTED

Test 11

Group: 2, 3

Verdict: ACCEPTED

Test 12

Group: 2, 3

Verdict: ACCEPTED

Test 13

Group: 2, 3

Verdict: ACCEPTED

Test 14

Group: 2, 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED

Test 17

Group: 3

Verdict: ACCEPTED

Test 18

Group: 3

Verdict: ACCEPTED

Test 19

Group: 3

Verdict: ACCEPTED

Test 20

Group: 3

Verdict: ACCEPTED

Test 21

Group: 3

Verdict: ACCEPTED