Monistus

#include <iostream>
#include <string>
#include <cstring>
using namespace std;

string gen[100000], res;
char inp[9], bString[1000], nString[9], rString[1000];
int indexSize;
bool dontContinue;
string build(string start, string insert, string end) {
    return start + insert + end;
}
string doCycle(string input) {
    dontContinue = true;
    for (int index = 0; index < int(input.size()); index++)
    {
        if (isdigit(input[index])) {
            memset(bString, 0, sizeof bString);
            memset(nString, 0, sizeof nString);
            memset(rString, 0, sizeof rString);
            dontContinue = false;
            for (int x = 0; x < index; x++) bString[x] = input[x];

            indexSize = input[index] - 48;
            for (int j = 1; j <= indexSize; j++) nString[j - 1] = input[index + j];
            for (int k = 1; (k + index) < int(input.size()); k++) rString[k - 1] = input[index + k];
            return build(bString, nString, rString);
        }
    }
    return input;
}
int main() {
    cin >> inp;
    gen[0] = doCycle(inp);
    for (int i = 1; i < 1000; i++) {
        gen[i] = doCycle(gen[i - 1]);
        if (dontContinue == true) {
            res = gen[i];
            break;
        }
    }
    cout << res;
    return 0;
}

Test 1

Group: 1, 2

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc

Test 2

Group: 1, 2

Verdict: WRONG ANSWER

Test 3

Group: 1, 2

Verdict: WRONG ANSWER

Test 4

Group: 1, 2

Verdict: WRONG ANSWER

Test 5

Group: 1, 2

Verdict: WRONG ANSWER

Test 6

Group: 1, 2

Verdict: WRONG ANSWER

Test 7

Group: 1, 2

Verdict: WRONG ANSWER

Test 8

Group: 2

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc

Test 9

Group: 2

Verdict: RUNTIME ERROR

free(): invalid pointer

Test 10

Group: 2

Verdict: WRONG ANSWER

Test 11

Group: 2

Verdict: WRONG ANSWER

Test 12

Group: 2

Verdict: WRONG ANSWER

Test 13

Group: 2

Verdict: RUNTIME ERROR

munmap_chunk(): invalid pointer

Test 14

Group: 2

Verdict: RUNTIME ERROR

terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc