Random string generation function

Author:火影

Wrote for play, Don't laugh at me!

#include "stdafx.h"
#include <stdio.h>
#include "windows.h"
#pragma comment(lib,"winmm.lib")

int main(int argc, char* argv[])
{
  int RanNum;
  int n1,n2;
  int count;
  char *buffer;
  char ch;
  //Generation seed
  srand((unsigned(timeGetTime())));
  RanNum=rand();
  n1=RanNum%10;
  printf("Random number%d\n",n1);
  n1++;
  buffer=(char *)VirtualAlloc(NULL,2*n1,MEM_COMMIT,PAGE_EXECUTE_READWRITE);
  memset((void *)buffer,0,2*n1);
  for (count=0;count<(2*n1-1);count++)
  {
    RanNum=rand();
    n2=RanNum%52;
    printf("Random number%d\n",n2);
    if (n2>=26)
    {
      ch=n2&0x0F;
      ch+=0x47;  //'a'------'z'
    }
    else
    {
      ch=n2&0x0F;
      ch+=0x41;  //'A'-----'Z'
    }
    buffer[count]=ch;
   
  }
  printf("Generate random string%s\n",buffer);
  VirtualFree(buffer,2*n1,MEM_DECOMMIT);
  return 0;
}

Prime factor resolve on C

 Author:Yangs

Maximum number is in favor of 4294967294, i.e. scanf("%lu") can go to maximum number.

Because resolve 4294967294 only to need prime table of 65535, Speed is more quickly.

In theory, 2.5×10^17 is resolved both short time. 2.5×10^17 need prime table of 500000000, My computer need 12.015 s

Code:
/**

 *   N*30+1, N*30+7, N*30+11, N*30+13, N*30+17, N*30+19, N*30+23, N*30+29

**/

#include "stdio.h"
#include "math.h"

long unsigned NUM;

char* real;;

long unsigned k;


inline void wtable(register unsigned long a)
{
    register unsigned long b;
    b=a/30;
    a=a%30;
    switch(a)
    {
      case 1:real[b]=real[b]&&!1;break;
      case 7:real[b]=real[b]&&!(1<<1);break;
      case 11:real[b]=real[b]&&!(1<<2);break;
      case 13:real[b]=real[b]&&!(1<<3);break;
      case 17:real[b]=real[b]&&!(1<<4);break;
      case 19:real[b]=real[b]&&!(1<<5);break;
      case 23:real[b]=real[b]&&!(1<<6);break;
      case 29:real[b]=real[b]&&!(1<<7);
      default:;
    }
}

inline int rtable(register unsigned long a)
{
  register unsigned long b;
  if(a>5)
  {
    b=a/30;
    if(real[b]==0)return 0;
    a=a%30;
    switch(a)
    {
      case 1:return real[b]&&1;
      case 7:return real[b]&&(1<<1);
      case 11:return real[b]&&(1<<2);
      case 13:return real[b]&&(1<<3);
      case 17:return real[b]&&(1<<4);
      case 19:return real[b]&&(1<<5);
      case 23:return real[b]&&(1<<6);
      case 29:return real[b]&&(1<<7);
      default:return 0;
    }
  }
  else
  {
    switch(a)
    {
      case 2:return 1;
      case 3:return 1;
      case 5:return 1;
      default:return 0;
    }
  }
}

void suShu()
{


  register unsigned long i=3,j,step;

  for(j=0; j<NUM/30+1; j++)
  {
    real[j] = 0xFF;//初始化数组
  }

  while(i<=k)
  {
  if(rtable(i)==0)
    {
      step=i<<1;
      for(j=i*i;j<=NUM;j+=step)
      wtable(j);
    }
    ++i;
    ++i;
  }

}


int main()
{
  unsigned long in;
  register unsigned long i;
  int f=0;
  printf("please inpout the No.:\n");
  scanf("%lu",&in);
  NUM=(unsigned long)sqrt((long double)in);
  real = new char[NUM/30+1];
  k = (long)sqrt((double)NUM);
  suShu();
  printf("%lu=",in);
  for (i=2;i<=NUM;i++)
  {
    if(rtable(i)==0)
      continue;
    else
    {
      if(in%i!=0)
        continue;
      else
      {
        in=in/i;
        i--;
        printf("%ld*",i+1);
        f=1;
      }
    }

  }
  if(in==1&f==1)printf("\b");
  else if(f==1)printf("%ld",in);
  else if(in<2)printf("\b can not factorization !");
  else printf("\b is prime number !");

  return 0;
}