Monistus

#include <iostream>
#include <unistd.h>
#include <string.h>

using namespace std;

typedef unsigned char u1;

int main() {

  u1 s[500000];

  cin >> s;

  unsigned long l = 0;
  while (s[++l] != '\0');

  for (u1 *c = s; *c != '\0';) {
    if (*c - (u1)'0' < 9) {
      unsigned long n = *c - '0';
      memmove(c + n, c + 1, l - (unsigned long)(c - s) - 1);
      memcpy(c, c + n, n);
      l += n;
    } else {
      c++;
    }
  }

  cout << s << endl;

  return 0;
}

Test 1

Group: 1, 2

Verdict: WRONG ANSWER

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: ACCEPTED

Test 4

Group: 1, 2

Verdict: ACCEPTED

Test 5

Group: 1, 2

Verdict: ACCEPTED

Test 6

Group: 1, 2

Verdict: ACCEPTED

Test 7

Group: 1, 2

Verdict: WRONG ANSWER

Test 8

Group: 2

Verdict: RUNTIME ERROR

*** stack smashing detected ***: terminated

Test 9

Group: 2

Verdict: RUNTIME ERROR

Test 10

Group: 2

Verdict: RUNTIME ERROR

Test 11

Group: 2

Verdict: WRONG ANSWER

Test 12

Group: 2

Verdict: RUNTIME ERROR

Test 13

Group: 2

Verdict: RUNTIME ERROR

Test 14

Group: 2

Verdict: RUNTIME ERROR