最大及最小素数.cpp

来自「一些经典程序」· C++ 代码 · 共 96 行

#include "math.h"

main()

/* max prime, min prime*/

{

long m,m1,i,k;

 for (m=100000002;m<=100001000;m+=6)

  {

    m1=m-1;

    k=sqrt(m1);

    for (i=3;i<=k;i+=2)

      if(m1%i==0) break;

    if(i>k)

     {

      printf("%ld is a prime\n",m1);

      break;

     }

    m1=m+1;

    k=sqrt(m1);

    for (i=3;i<=k;i+=2)

      if(m1%i==0) break;

    if(i>k)

     {

     printf("%ld is a prime\n",m1);

     break;

     }

   }

    for (m=999999998;m>=999999000;m-=6)

  {

    m1=m+1;

    k=sqrt(m1);

    for (i=3;i<=k;i+=2)

      if(m1%i==0) break;

    if(i>k)

     {

      printf("%ld is a prime\n",m1);

      break;

     }

    m1=m-1;

    k=sqrt(m1);

    for (i=3;i<=k;i+=2)

      if(m1%i==0) break;

    if(i>k)

     {

     printf("%ld is a prime\n",m1);

     break;

     }

   }

   }