Codeforces Round 921 (Div. 2) 1925C. Did We Get Everything Covered? Solution

 Problem Link :  https://codeforces.com/contest/1925/problem/C 

Solution in C++:

1. /// Author : AH_Tonmoy
2. #include <bits/stdc++.h>
3. using namespace std;
4. int32_t main() {
5. ios_base::sync_with_stdio(0);
6. cin.tie(0);
7. int t;
8. cin >> t;
9. while (t--) {
10. int n , k , m ; cin >> n >> k >> m ;
11. string s ; cin >> s ;
12. string ans ="";
13. set<char>st ;
14. for (int i = 0 ; i < m ; i++){
15. st.insert(s[i]) ;
16. if(st.size() == k ){
17. ans +=s[i] ;
18. st.clear() ;
19. }
20. }
21. if(ans.size() >= n){
22. cout <<"YES\n";
23. }
24. else{
25. cout <<"NO\n" ;
26. char mis_ch ;
27. for( int i = 0 ; i < k ; i++){
28. char c = (char)('a'+i) ;
29. if(st.count(c) == 0){
30. mis_ch = c ;
31. break ;
32. }
33. }
34. while(ans.size() < n) {
35. ans += mis_ch ;
36. }
37. cout << ans <<'\n';
38. }
39. }
40. return 0 ;
41. }