Sukat

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector <ll> vl;
typedef vector <vl> vvl;
typedef pair <ll, ll> pl;
typedef vector <pl> vpl;
typedef vector <bool> vb;

const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ll nmax = 1e6;

#define fi first
#define se second
#define mp make_pair
#define pb push_back

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

    string s;
    vpl a(26, {0, 0});
    ll l, i, j;
    cin >> s;
    l = s.length();
    for(i = 0; i < l; i++)
        a[s[i] - 'A'].fi++;
    for(i = 0; i < 26; i++)
        a[i].se = i;

    sort(a.begin(), a.end(), greater<pl>());

    cout << min(l / 2, l - a[0].fi) << "\n";

    if(l - a[0].fi <= l / 2)
        for(i = 1; i < 26; i++)
            while(a[i].fi > 0)
            {
                cout << char(a[0].se + 'A') << char(a[i].se + 'A') << "\n";
                a[i].fi--;
            }
    else
    {
        j = 0;
        for(i = 0; i < 26; i++)
            while(a[i].fi > 0)
            {
                s[j] = char(a[i].se + 'A');
                j++;
                a[i].fi--;
            }
        for(i = 0; i < l / 2; i++)
            cout << s[i] << s[i + l / 2] << "\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