Sukat

#include<bits/stdc++.h>
using namespace std;
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define fi first
#define se second
#define pii pair<int,int>
using ll = long long;

int f[26];

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    string s;
    cin >> s;

    for (char c : s) f[c-'A']++;
    
    priority_queue<pair<int, char>> pq;
    for (char c = 'A'; c <= 'Z'; c++) if (f[c-'A']) pq.push({f[c-'A'], c});

    vector<pair<char, char>> ans;
    while (pq.size() > 1) {
        auto [f1, c1] = pq.top(); pq.pop();
        auto [f2, c2] = pq.top(); pq.pop();
        ans.push_back({c1, c2});
        f1--; f2--;
        if (f1) pq.push({f1, c1});
        if (f2) pq.push({f2, c2});
    }

    cout << ans.size() << "\n";
    for (auto u : ans) cout << u.fi << u.se << "\n";
    
    return 0;
}

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