標記素數法（模板）+素數打表

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#include <stdio.h>#include <string.h>#define N 3000000int f[3000000];int main(){memset(f, 0, sizeof(f));int i, j;f[0]=1;f[1]=1;for(i=2; i<=N; i++){if(f[i]==0){for(j=i*2; j<=N; j+=i){f[j]=1; //不是素數}}} // 列印所有發f[i]==0, 即為素數for(i=2; i<=N; i++){if(f[i]==0)printf("%d  ", i );}return 0;}

 

#include <stdio.h>#include <string.h>#include <math.h>#define N 3000000int c=0;int f[3000000];int prime[1000000];int main(){int i, j;    memset(f, 0, sizeof(f));f[0]=1;f[1] =1;for(i=2; i<=N; i++){if(f[i]==0){prime[c++] = i;for(j=2*i; j<=N; j+=i ){f[j]=1;}}}for(i=0; i<=1000; i++){printf("%d  ", prime[i] );}return 0;}

 素數打表法二：

#include<stdio.h>  #include<string.h>  #define N 1000005int prime[100005];  int flag[1000005];  int e;  void getP()  // 素數打表,找出素數存棧  {  int i, j;  e = 0;  memset(flag, 0, sizeof(flag) ); //標記初始化for ( i=2; i<N; i++)  {  if ( flag[i]==0 ) {prime[e++] = i; //進棧  }for ( j=0; j<e && i*prime[j]<N; j++ )  {  flag[ i * prime[j] ] = 1;  }  }  }