/*/ problem source:
 * https://www.geeksforgeeks.org/find-the-longest-substring-with-k-unique-characters-in-a-given-string/
 */
#include <iostream>
#include <ostream>
#include <unordered_map>
#include <vector>

class result {
public:
  unsigned long longest_start = 0;
  unsigned long longest_end = 0;
  bool match_found = false;
  bool operator==(const result r) {
    return longest_start == r.longest_start && longest_end == r.longest_end &&
           match_found == r.match_found;
  };
};

struct input {
  std::string s;
  unsigned long k;
};

struct test_case {
  input i;
  result r;
};

result find(const std::string &s, const unsigned long k) {
  result r;
  std::unordered_map<char, unsigned long> char_count;
  unsigned long start = 0, end = 0;
  for (; end < s.length(); end++) {
    char_count[s[end]] += 1;
    while (char_count.size() > k) {
      char_count[s[start]]--;
      if (char_count[s[start]] == 0) {
        char_count.erase(s[start]);
      }
      start++;
    }
    if (char_count.size() == k &&
        end - start > r.longest_end - r.longest_start) {
      r.longest_start = start, r.longest_end = end;
      r.match_found = true;
    }
  }

  if (r.match_found) {
    std::cout << "Longest substring is \""
              << s.substr(r.longest_start, r.longest_end - r.longest_start + 1)
              << "\" with length " << r.longest_end - r.longest_start + 1
              << ".\n";
  } else {
    std::cout << "Could not find any match, not enough unique characters.\n";
  }
  return r;
}

int main() {
  std::vector<test_case> test_cases = {{{"aabacbebebe", 3}, {4, 10, true}},
                                       {{"aabbcc", 1}, {0, 1, true}},
                                       {{"aabbcc", 3}, {0, 5, true}},
                                       {{"aaabbb", 3}, {0, 0, false}}};
  for (const test_case &t : test_cases) {
    if (find(t.i.s, t.i.k) == t.r) {
      std::cout << "Test case with string \"" << t.i.s << "\" and k=" << t.i.k
                << " passed.\n";
    } else {
      std::cout << std::flush;
      std::cerr << "TEST CASE WITH STRING \"" << t.i.s << "\" AND k=" << t.i.k
                << " FAILED.\n";
    }
  }
  return 0;
}