Monistus

#include<iostream>
#include<bits/stdc++.h>
#include<string> 
#include<map>
#include <unordered_map>
#include<deque>
using namespace std;
 
typedef long long ll;
 
constexpr ll M = 1000000007;
constexpr ll P = (1 << 18);
constexpr int INF = 1e9;
 
int seenCount;
int depth;
int maxSize;
 
unordered_map<string, string> m;

string solve(string input, int length) {
	string key = to_string(length) + input.substr(0, length);
	if (m.count(key)) {
		seenCount++;
		return m[key];
	}

	string res;
	//int n = input.size();

	bool memoize = true;
	for (int i=0; i<length; i++) {
		char ch = input[i];
		int digit = ch - '0'; 
 
		if (digit > 0 && digit <= 9) {
			string cutout = input.substr(i+1, digit);
			//cout << "cutout: " << cutout << endl;
			string expanded = solve(cutout + cutout, digit); 
			//cout << "exp: " << expanded << endl;
			res += expanded;

			string normal = solve(input.substr(i+1, digit+digit), digit);

			int overlap = (i + digit) - length + 1; 
			while (overlap > 0) {
				memoize = false;
				normal.pop_back();
				overlap--;
			}
			res += normal;

			i += digit;
		} else {
			res += ch;
		}
	}

	//cout << "res for " << input << ": " << res << endl;

	if (memoize) m[key] = res;
	return res;
}
 
vector<char> ans;

int main() {
	ans.reserve(501010);

	string prompt;
	cin >> prompt;

	//cout << solve(prompt, (int)prompt.size());

	for (int i=0; i<(int)prompt.size(); i++) {
		char ch = prompt[i];
		int digit = ch - '0'; 
 
		if (digit > 0 && digit <= 9) {
			string cutout = prompt.substr(i+1, digit);
			//cout << "cutout: " << cutout << endl;
			string expanded = solve(cutout + cutout, digit); 
			//cout << "exp: " << expanded << endl;
			ans.insert(ans.end(), expanded.begin(), expanded.end());

			string normal = solve(prompt.substr(i+1, digit+digit), digit);
			ans.insert(ans.end(), normal.begin(), normal.end());

			i += digit;
		} else {
			ans.push_back(ch);
		}
	}

	for (auto ch : ans) cout << ch;
	cout << endl;

	//cout << "-==================|" <<endl;
	//for (auto x : m) {
	//	cout << x.first << ": " << x.second << endl;
	//}
	//cout << seenCount << endl;

	//cout << maxSize << endl;
	//cout << ans.size() << endl;
}

Test 1

Group: 1, 2

Verdict: ACCEPTED

Test 2

Group: 1, 2

Verdict: ACCEPTED

Test 3

Group: 1, 2

Verdict: WRONG ANSWER

Test 4

Group: 1, 2

Verdict: ACCEPTED

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: ACCEPTED

Test 9

Group: 2

Verdict: RUNTIME ERROR

Test 10

Group: 2

Verdict: RUNTIME ERROR

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED