HDU 1402 A * B Problem Plus

这是大数相乘的一模板题;

先把两个字符串变成ASCII码(不能和倒置放在一块,否则会出错),然后把他们全部倒置,然后再将他们相乘,最后再进位,不过这样会超时,将会在近段时间内发布不超时的代码

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define Max 100000
int num[Max];
char str1[Max] = {0},str2[Max] = {0};
void cal( )
{
     int len1 = strlen( str1 ),len2 = strlen( str2 );
     for( int i = 0; i < ( len1 > len2 ? len1 : len2 ); ++i )
          str1[i] -= '0',str2[i] -= '0';
     for( int p = 0,q = len1 - 1; q > p; --q,++p ) 
     {
          char c = str1[q];
          str1[q] = str1[p];
          str1[p] = c;
      }
      for( int p = 0, q = len2 - 1; q > p; --q,++p )
      {
           char c = str2[q];
           str2[q] = str2[p];
           str2[p] = c;
       }
     for( int i = 0; i < len1 ; ++i )
          for( int j = 0; j < len2; ++j )
               num[i + j] = str1[i] * str2[j];
     int i = Max;
     while( !num[--i] );
     for( int j = 0,c = 0; j <= i||c; ++j )
     {
          c += num[j];
          num[j] = c % 10;
          c /= 10;
      }
 }
int main( )
{
    while( scanf( "%s%s",str1,str2 ) != EOF )
    {
           memset( num,0,sizeof( num ) );
           cal(  );
           int n = Max;
           while( !num[--n] );
           while( n >= 0 )
                  printf( "%d",num[n--] );
           puts( "" );
           memset( str1,0,sizeof( str1 ) );
           memset( str2,0,sizeof( str2 ) );
           }
    return 0;
}