Pakkaus

#include <iostream>
#include <string>

using std::string;
using std::stoi;
using std::cout;
using std::endl;
using std::cin;

size_t pos_next(bool b, size_t pos, string &s) {
// b true returns next number
// b false returns next str

  for (; pos < s.length(); pos++) {
    if (s[pos] == '0' || s[pos] == '1' || s[pos] == '2' || s[pos] == '3' || s[pos] == '4' || s[pos] == '5' || s[pos] == '6' || s[pos] == '7' || s[pos] == '8' || s[pos] == '9') {
      if (b) {
        return pos;
      }
    } else {
      if (!b) {
        return pos;
      }
    }
  }
  
  return pos;
}

int main(int argc, char** argv) {
 /* if (argc != 2) {
    cout << "invalid input\n";
    return -1;
  }*/

  //string s = string(argv[1]);
  string s;
  cin >> s;
  size_t pos = 0;  
  size_t n_start = 0;
  size_t t_start = 0;
  size_t t_end = 0;

  while(true) {
    n_start = pos_next(true, pos, s);
    t_start = pos_next(false, n_start, s);

    int n = stoi(s.substr(n_start, t_start-n_start));

    t_end = pos_next(true, t_start, s);
    string t = s.substr(t_start, t_end-t_start);

    pos = t_end;
    
    for (; n > 0; n--) {
      cout << t;
    }

    if (pos == s.length()) {
      cout << endl;
      return 0;
    }
  }

  return 0;
}

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: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED