Submission #1257646

#	Time	Username	Problem	Language	Result	Execution time	Memory
1257646		kargneq	Hack (APIO25_hack)	C++20	Compilation error	0 ms	0 KiB

hack

long long hack() {
  const long long M = 1000000;
  vector<long long> x(M);
  iota(x.begin(), x.end(), 1);
  long long C = collisions(x);  // one query

  for (long long q = 0; q <= M/2; ++q) {
    long long denom = q * (q + 1) / 2;        // C(q+1,2)
    if (denom == 0) continue;                 // q=0 impossible when n>=2 and M>=1
    long long numer = M * q - C;
    if (numer <= 0) continue;
    if (numer % denom) continue;              // must divide
    long long n = numer / denom;
    if (n >= 2 && M / n == q)                 // floor(M/n) == q
      return n;
  }
  // If you’re paranoid, fall back to smaller M or different set, but this loop finds it.
  return 2; // unreachable for valid tests
}

Compilation message (stderr)

hack.cpp: In function 'long long int hack()':
hack.cpp:3:3: error: 'vector' was not declared in this scope
    3 |   vector<long long> x(M);
      |   ^~~~~~
hack.cpp:3:10: error: expected primary-expression before 'long'
    3 |   vector<long long> x(M);
      |          ^~~~
hack.cpp:4:8: error: 'x' was not declared in this scope
    4 |   iota(x.begin(), x.end(), 1);
      |        ^
hack.cpp:4:3: error: 'iota' was not declared in this scope
    4 |   iota(x.begin(), x.end(), 1);
      |   ^~~~
hack.cpp:5:17: error: 'collisions' was not declared in this scope
    5 |   long long C = collisions(x);  // one query
      |                 ^~~~~~~~~~