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  1. #include <stdio.h>
  2. #include <string.h>
  3.  
  4. #define ISBITSET(x, i) (( x[i>>3] & (1<<(i&7)) ) != 0)
  5. #define SETBIT(x, i) x[i>>3] |= (1<<(i&7));
  6. #define CLEARBIT(x, i) x[i>>3] &= (1<<(i&7)) ^ 0xFF;
  7.  
  8. long long sumPrimes(int n) {
  9.     char b[n/8+1];
  10.     long long i, p;
  11.     long long s = 0;
  12.  
  13.     memset(b, 255, sizeof(b));
  14.     for (p=2; p<n; p++) {
  15.         if (ISBITSET(b,p)) {
  16.             //printf("%d\n", p);
  17.             s += p;
  18.             for (i=p*p; i<n; i+=p) {
  19.                 CLEARBIT(b, i); }}}
  20.     return s; }
  21.  
  22. int main(void) {
  23.     printf("%lld\n", sumPrimes(2000000));
  24.     return 0; }
Success #stdin #stdout 0.03s 2416KB
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142913828922
https://ideone.com/2NRLTz
language:
C (gcc 8.3)
created:
11 years ago
visibility:
public

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