isPrime function

bool isPrime(
  1. int n
)

Checks if a given number n is prime.

Uses an optimized 6k +/- 1 check algorithm.

Implementation

bool isPrime(int n) {
  if (n <= 1) return false;
  if (n <= 3) return true;
  if (n % 2 == 0 || n % 3 == 0) return false;

  for (int i = 5; i * i <= n; i += 6) {
    if (n % i == 0 || n % (i + 2) == 0) return false;
  }
  return true;
}