Ositus

#include <bits/stdc++.h>

using namespace std;

#define M 1000000007

#define SUM(x) (x*(x+1)/2)

string s;
int n,r;

int sum(int f)
{
    if(f==n) return 1;
    int o = 0;
    set<char> t;
    while(t.count(s[f])==0 && f<n)
    {
        t.insert(s[f]);
        f++;
        o += sum(f);
    }
    return o;
}

int main()
{
    cin>>s;
    n = s.size();
    cout<<sum(0);
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 2, 3

Verdict: TIME LIMIT EXCEEDED

Test 6

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 7

Group: 3

Verdict: TIME LIMIT EXCEEDED