Monistus

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

string get(string s, ll &i, ll l)
{
    ll e = i + s[i] - '0', j = i + 1, x = i;
    while(j <= e)
    {
        if(s[j] < 'a')
            e = max(j + s[j] - '0', e);
        j++;
    }
    i = j;
    //cout << i << " ";
    return s.substr(x, j - x);
}

string work(string a, ll l)
{
    ll i, d, j = 0;
    vector <string> s(2);
    s[j] = a;
    for(i = 0; i < l; i++)
        if(s[j][i] < 'a')
        {
            d = s[j][i] - '0';
            s[1 - j] = s[j].substr(0, i) + s[j].substr(i + 1, d) + s[j].substr(i + 1, d) + s[j].substr(i + 1 + d, l - i - d - 1);
            l += d - 1;
            i--;
            j = 1 - j;
        }
    return s[j];
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0); cout.tie(0);

    string s, ans, temp, k;
    bool check = false;
    ll l, b = 0, i = 0;

    cin >> s;
    l = s.length();
    while(i < l)
    {
        while(i < l && s[i] >= 'a')
            i++;
        ans += s.substr(b, i - b);
        if(i == l)
            break;
        //cout << i << " " << ans << "\n";

        temp = get(s, i, l - 1);
        //cout << temp << "\n";
        k = work(temp, temp.length());
        //cout << i << " " << temp << " " << k << "\n";
        ans += k;
        //cout << ans << "\n";

        b = i; check = true;
    }

    if(!check)
        cout << s;
    else
        cout << ans;

    return 0;
}

//uyo7iuoy6khv4fcytgib3tr21as

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