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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.     int m = (n-1) / 2;
  10.     char b[m/8+1];
  11.     int i = 0;
  12.     int p = 3;
  13.     long long s = 2;
  14.     int j;
  15.  
  16.     memset(b, 255, sizeof(b));
  17.  
  18.     while (p*p < n) {
  19.         if (ISBITSET(b,i)) {
  20.             s += p;
  21.             j = (p*p - 3) / 2;
  22.             while (j < m) {
  23.                 CLEARBIT(b, j);
  24.                 j += p; } }
  25.         i += 1; p += 2; }
  26.  
  27.     while (i < m) {
  28.         if (ISBITSET(b,i)) {
  29.             s += p; }
  30.         i += 1; p += 2; }
  31.  
  32.     return s; }
  33.  
  34. int main(void) {
  35.     printf("%lld\n", sumPrimes(2000000));
  36.     return 0; }
Success #stdin #stdout 0s 2292KB
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142913828922
https://ideone.com/2fkX4Y
language:
C (gcc 8.3)
created:
11 years ago
visibility:
public

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