HDU 1164 Eddy's research I

题意：把一个数拆成素数，从小到大排列。如果把素数全部存起来大概快一半的样子

#include<stdio.h>
#include<string.h>
#define Max 65540
int n,prime[Max+5],num[Max],c = 0;
void DFS( int x )
{
     if( x == 0 )
         return ;
     for( int i = 0; i < c; ++i )
     {
          if( x % num[i] == 0 )
          {
              printf( x == n?"%d":"*%d",num[i] );
              DFS( x / num[i] );
              break;
          }
     }
 }
int main(  )
{
    memset( prime,0,sizeof( prime ) );
     prime[0] = prime[1] = 1;
     for( int i = 2; i <= Max / 2; ++i )
          if( !prime[i] )
              for( int j = i + i; j <= Max; j += i )
                    prime[j] = 1;
     for( int i = 2; i <= Max; ++i )
          if( !prime[i] )
              num[c++] = i;
    while( scanf( "%d",&n ) != EOF )
           DFS( n ),puts( "" );
    return 0;
}