Ositus

#include <bits/stdc++.h>
#include <iterator>
#include <unordered_set>

using namespace std;

int main() {
  int result = 0;
  string s; cin >> s;
  int n = s.length();
  vector<int> points(n, 0);
  unordered_set<char> seen;

  auto left = s.begin();
  auto right = left+1;

  while (left < s.end()) {
    int i = distance(s.begin(), right);

    if (seen.count(*right) == 0 && right != s.end()) {
      if (seen.empty()) seen.insert(*left);

      seen.insert(*right);
      ++points[i];
      ++right;
    } else {
      if (!seen.empty()) seen.clear();
      ++left;
      right = left+1;
    }
  }

  for (int i = 1; i < n; ++i) points[i] += points[i-1];

  seen.clear();
  left = s.begin();
  right = left+1;

  vector<int> finals(n, 0);

  while (left < s.end()) {
    int i = distance(s.begin(), left);
    int j = distance(s.begin(), right);

    if (seen.count(*right) == 0 && right != s.end()) {
      if (seen.empty()) seen.insert(*left);

      int p = 1;
      if (i>1) p += points[i-1];

      seen.insert(*right);
      finals[j] += p;
      ++right;
    } else {
      if (!seen.empty()) seen.clear();
      ++left;
      right = left+1;
    }
  }

  for (int i = 1; i < n; ++i) {
    finals[i] += finals[i-1];
  }

  seen.clear();
  
 for (int i = n-1; i > 0; --i) {
    char val = s[i];
    if (seen.count(val) != 0) break;

    int p = finals[i-1]+1;
    result += p;
    seen.insert(val);
  }

  cout << result%1000000007 << endl;
}

Test 1

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 2

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 3

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 4

Group: 1, 2, 3

Verdict: WRONG ANSWER

Test 5

Group: 2, 3

Verdict: WRONG ANSWER

Test 6

Group: 3

Verdict: WRONG ANSWER

Test 7

Group: 3

Verdict: WRONG ANSWER