Pakkaus

import java.util.Scanner;

public class Pakkaus {

    public static void main(String[] args) {
        
        char[] compressed = new Scanner(System.in).nextLine().toCharArray();
        
        StringBuilder uncompressed = new StringBuilder();
        
        int i = 0;
        while(i < compressed.length){
            String kString = "";
            while(Character.isDigit(compressed[i])){
                kString += compressed[i];
                i++;
            }
            int k = Integer.parseInt(kString);
            
            String s = "";
            while(i < compressed.length && !Character.isDigit(compressed[i])){
                s += compressed[i];
                i++;
            }
            
            for(int j = 0; j < k; j++){
                uncompressed.append(s);
            }
        }
        
        System.out.println(uncompressed.toString());
    }
    
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED