Sukat

input/code.cpp: In function 'int main()':
input/code.cpp:15:23: warning: comparison of integer expressions of different signedness: 'int' and 'size_t' {aka 'long unsigned int'} [-Wsign-compare]
   15 |     for (int i = 0; i < strlen(s); i++) {
      |                     ~~^~~~~~~~~~~
input/code.cpp:59:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<char, char> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   59 |     for (int i = 0; i < res.size(); i++) {
      |                     ~~^~~~~~~~~~~~
input/code.cpp:14:10: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   14 |     scanf("%s", s);
      |     ~~~~~^~~~~~~~~

#include <bits/stdc++.h>
using namespace std;

#define CHARS 26

priority_queue<pair<int, int>> nums;
int start[CHARS];
char s[1000000];

int main()
{
    vector<pair<char, char>> res;

    scanf("%s", s);
    for (int i = 0; i < strlen(s); i++) {
        char c = s[i];

        int a = c - 'A';
        start[a]++;
    }

    for (int i = 0; i < CHARS; i++) {
        if (start[i] > 0) {
            nums.push(make_pair(start[i], i));
        }
    }

    while (!nums.empty())
    {
        //cerr << nums.size() << endl;
        pair<int, int> a = make_pair(nums.top().first, nums.top().second);
        nums.pop();

        if (nums.empty()) {
            break;
        }

        pair<int, int> b = make_pair(nums.top().first, nums.top().second);
        nums.pop();
        b.first -= 1;
        a.first -= 1;
        res.push_back(make_pair(b.second + 'A', a.second + 'A'));

        if (b.first != 0) {
            nums.push(b);
        }

        if (a.first != 0) {
            nums.push(a);
        }
    }

    for (int i = 0; i < CHARS; i++) {
        //cerr << nums[i] << endl;
    }

    cout << res.size() << endl;

    for (int i = 0; i < res.size(); i++) {
        cout << res[i].first << res[i].second << 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: 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