Guest User

sieve_erastothenes_C

a guest
Jul 23rd, 2013
83
Never
Not a member of Pastebin yet? Sign Up, it unlocks many cool features!
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <math.h>
  4.  
  5. int main(int argc, char const *argv[]) {
  6. if (argc != 2) {
  7. printf("Usage: sieve N, where N is the desired maximum value for the sieve.\n");
  8. return -1;
  9. }
  10.  
  11. int N = (unsigned long long) strtoull(argv[1], NULL, 10);
  12.  
  13. // Stop sieve at sqrt of max # in sieve, because all non-primes are
  14. // already gone.
  15. int M = (int) sqrt((double) N);
  16.  
  17. if (N < 0) {
  18. printf("N must be positive.\n");
  19. return -1;
  20. }
  21. if (N < 2) {
  22. printf("No primes.\n");
  23. return 0;
  24. }
  25.  
  26. int * primes;
  27. primes = calloc(N, sizeof(int));
  28.  
  29. // 0 is untouched, 1 is not prime
  30. printf("2\n");
  31. for (int i = 3; i <= M; i=i+2) {
  32. if (primes[i] == 1) continue;
  33. printf("%d\n", i);
  34. for (int j = i * i; j <= N; j=j+i) {
  35. if (primes[j] == 1) continue;
  36. primes[j] = 1;
  37. }
  38. }
  39. if (!(M % 2)) M = M + 1;
  40. for (int i = M; i <= N; i=i+2) {
  41. if (primes[i] == 0) {
  42. printf("%d\n", i);
  43. }
  44. }
  45.  
  46. return 0;
  47. }
RAW Paste Data

Adblocker detected! Please consider disabling it...

We've detected AdBlock Plus or some other adblocking software preventing Pastebin.com from fully loading.

We don't have any obnoxious sound, or popup ads, we actively block these annoying types of ads!

Please add Pastebin.com to your ad blocker whitelist or disable your adblocking software.

×