Ositus

#include <algorithm>
#include <map>
#include <iostream>
#include <set>
#include <string> 

using namespace std;

long long M = 1e9 + 7;


map<string, long long> lookupTable;

long long f(string s) {
    string substr, tail;
    long long v = 0;
    if (s.size() <= 1) {
        return 1;
    }
    if (lookupTable.count(s)) {
        return lookupTable[s];
    }
    // int i = find(s.rend()-1, s.rbegin(), s[s.size()-1]);

    for (unsigned int i=1; i<=s.size(); i++) {
        substr = s.substr(0, s.size()-i), tail = s.substr(s.size()-i, i);

        if (set<char>(tail.begin(), tail.end()).size() != tail.size())
            break;
        v += f(substr);
        v %= M;
    }

    lookupTable[s] = v;
    return v;

}


int main() {
    string s;

    cin >> s;

    cout << f(s);

}

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: ACCEPTED

Test 6

Group: 3

Verdict: ACCEPTED

Test 7

Group: 3

Verdict: RUNTIME ERROR