Ositus

#include <bits/stdc++.h>

using namespace std;

#define M 1000000007

typedef long long int ll;

string s;
ll r;
map<char,ll> m;

int main()
{
    cin>>s;
    ll pf = 0;
    ll pl = 0;
    for(char c : s)
    {
        if(r == 0)
        {
            r++;
        }
        else
        {
            r *= 2;
            if(m[c]>0)
            {
                if(pl<=m[c])
                {
                    r -= m[c];
                }
                else if(pf<=m[c])
                {
                     r -= pl-m[c];
                }
                pf = m[c];
                pl = r;
            }

        }
        r %= M;
        m[c] = r;
    }
    if(r<0) r += M;
    cout<<r;
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 2, 3

Verdict: WRONG ANSWER

Test 6

Group: 3

Verdict: WRONG ANSWER

Test 7

Group: 3

Verdict: WRONG ANSWER