Monistus

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll n, q, m, a, b, c;
vector<pair<int,int>> v[202020];
int e[202020];
set<int> se;
string s;

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cin >> s;
	int i=0;
	int pit=s.length();
	string alku="";
	while(i<pit) {
		//int apu=s[i]-'1';
		//cout << apu << "\n";
		if (s[i]<='9' && s[i]>='1') {
			int num = s[i]-'0';
			q=pit;
		//	string alku = s.substr(0,i);
		//	cout << "i: " << i << "\n";
		//	cout << "alku: " <<  alku << "\n";
			string keski = s.substr(i+1,num);
			string loppu = s.substr(i+1+num,q-i-1);
		//	cout << "keski: " << keski << "\n";
		//	cout << "loppu: " <<  loppu << "\n";
		//	alku=alku+keski+keski;
			s=alku+keski+keski+loppu;
			pit+=num-1;
		} else {
			alku+=s[i];
			i++;
		//	cout << pit << "\n";
		}
	}
//	cout << s.length() << "\n";
	cout << s << "\n";
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

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: ACCEPTED

Test 8

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 9

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 10

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 11

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 12

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 13

Group: 2

Verdict: TIME LIMIT EXCEEDED

Test 14

Group: 2

Verdict: TIME LIMIT EXCEEDED