Sukat

#include <bits/stdc++.h>

using namespace std; 

string s;
int n;
map<char, int > m;
set<pair<int, char>> p;
vector<pair<char, char>> ans;

int main(){
    cin >> s;
    n = s.length();
    for(int i = 0; i < n; i++) m[s[i]]++;

    for(auto i : m) p.insert({i.second, i.first});


    while(p.size() > 1){
        cout << endl; 
        int x = p.rbegin()->first; char c = p.rbegin()->second;
        auto it = p.end(); it--;
        p.erase(it);
        int y = p.rbegin()->first; char g = p.rbegin()->second;
        it = p.end(); it--;
        p.erase(it);
        if(x > 1) p.insert({x - 1, c});
        if(y > 1) p.insert({y - 1, g});
        ans.push_back({c, g});
    }
    
    cout << ans.size() << endl;
    for(auto i : ans) cout << i.first << " " << 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