Monistus

#include <bits/stdc++.h>

using namespace std;
using ull = uint64_t;
using sll = int64_t;
static const ull inf = UINT64_MAX;
static const sll infs = INT64_MAX;

using vu = vector<ull>;
using pu = pair<ull, ull>;

string* next(list<string*>::iterator ent, ull index)
{
	string* res = new string();
	ull l = (**ent)[index] - '0';
	res->reserve(l);
	ull cur = index + 1;
	ull i = 0;
	while (i < l)
	{
		//cout << l << " " << cur << " " << i << " " << (**ent) << " " << *res << endl;
		if (cur + (l - i) <= (*ent)->size())
		{
			res->append(**ent, cur, (l - i));
			i = l;
		}
		else
		{
			res->append(**ent, cur);
			i += (*ent)->size() - cur;
			++ent;
			cur = 0;
		}
		//cout << "go" << endl;
		//if (cur >= (*ent)->size() - 1)
		//{
		//	++ent;
		//	cur = 0;
		//}
		//else
		//{
		//	++cur;
		//}
		////cout << "P" << (*ent)[cur] << endl;
		//res->push_back((**ent)[cur]);
	}
	//cout << *res << endl;
	//cout << "hey" << endl;
	return res;
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	list<string*> rope;
	string* inp = new string();
	getline(cin, *inp);
	rope.push_back(inp);

	string res;
	res.reserve(1000000);

	auto it = rope.begin();
	ull index = 0;
	while (it != rope.end())
	{
		char chr = (**it)[index];
		if (chr < '0' || chr > '9')
		{
			//cout << chr;
			if (index >= (*it)->size() - 1)
			{
				res.append(**it);
				delete *it;
				++it;
				rope.erase(prev(it));
				index = 0;
			}
			else
			{
				++index;
			}
		}
		else
		{
			//cout << "Current rope state:" << endl;
			//auto sit = rope.begin();
			//while (sit != rope.end())
			//{
			//	cout << *sit++ << endl;
			//}
			//cout << chr << endl;
			string* nxt = next(it, index);
			//cout << nxt << endl;
			if (index + 1 < (*it)->size())
			{
				string* rest = new string((*it)->begin() + index + 1, (*it)->end());
				rope.insert(next(it), rest);
			}
			rope.insert(next(it), nxt);
			res.append(**it, 0, index);
			delete *it;
			++it;
			rope.erase(prev(it));
			index = 0;
			//auto sit = rope.begin();
			//while (sit != rope.end())
			//{
			//	cout << *sit++;
			//}
			//cout << endl;
		}
	}

	//it = rope.begin();
	//while (it != rope.end())
	//{
	//	cout << *it++;
	//}
	cout << res;
	cout << endl;
}

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: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

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