Envío 2182

Código

#include <iostream>
#include <vector>
#include <cassert>
#include <set>
#include <unordered_set>
using namespace std;

int main() {
  string s;
  cin >> s;
  int n = s.size();
  assert(1 <= n and n <= 100000);
  int k;
  cin >> k;
  assert(1 <= k and k <= 26);

  int best = -1;
  for (int i = 0; i < n; i++) {
    unordered_set<char> seen;
    for (int j = i; j < n; j++) {
      seen.insert(s[j]);
      if (seen.size() > k) {
        break;
      }

      best = max(best, j - i + 1);
    }
  }
  cout << best << endl;
  return 0;
}