Monistus

#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vl;


int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    const int N = 500005;
    string s; cin >> s;
    int n = s.size();
    vector<char> v(N, '-');
    for(int i = 0; i < n; i++) v[N - n + i] = s[i];
    int i = N - n;
    string ans = "";
    while(i < N){
        if(v[i] <= 122 && v[i] >= 97) ans += v[i];
        else{
            int x = v[i] - '0';
            for(int j = i + 1; j < i + x + 1; j++){
                v[j-x] = v[j];
            }
            i = i - x;
        }
        i++;
    }    
    cout << ans << "\n";
    return 0;
}


/*
auto start = std::chrono::high_resolution_clock::now();
auto end = std::chrono::high_resolution_clock::now();
cout << "TIME: " << std::chrono::duration_cast<std::chrono::milliseconds>(end-start).count() / 1000.0 << "\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: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED