17 lines
398 B
C
17 lines
398 B
C
int isPrime(int n) {
|
|
|
|
// returns 0 if not prime, 1 if prime
|
|
|
|
if (n<2) return 0; // first prime number is 2
|
|
if (n==2) return 1; // ensure 2 is identified as a prime
|
|
if ((n % 2)==0) return 0; // all even numbers above 2 are not prime
|
|
|
|
int i;
|
|
for (i=3; i*i < n; i++) { // test divisibility up to sqrt(n)
|
|
if ((n % i) == 0) {
|
|
return 0;
|
|
}
|
|
}
|
|
return 1;
|
|
}
|