UVA 10106 Product（大数乘法）

The Problem

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The problem is to multiply two integers X,Y. (0<=X,Y<10250)
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The Input

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The input will consist of a set of pairs of lines. Each line in pair contains one multiplyer.
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The Output

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For each input pair of lines the output line should consist one integer the product.
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Sample Input

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?12
12
2
222222222222222222222222
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Sample Output

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?144
444444444444444444444444

代码：

#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>

using namespace std;

void bigmul(char *a,char *b,char *c)
{
    int la,lb,lc,i,j,aa[1000],bb[1000],cc[3000],t,n;
    la=strlen(a)-1;
    lb=strlen(b)-1;
    for(i=la,j=0;i>=0;i--)  aa[j++]=a[i]-'0';
    for(i=lb,j=0;i>=0;i--)  bb[j++]=b[i]-'0';
    memset(cc,sizeof(cc));
    for(i=0;i<=la;i++)
        for(j=0;j<=lb;j++)
           cc[i+j]+=aa[i]*bb[j];
    for(i=0;i<=la+lb+5;i++)
    {  t=cc[i]/10;
        cc[i+1]+=t;
        cc[i]=cc[i]-t*10;}
    for(i=la+lb+5;i>=0;i--)
          if(cc[i]!=0)
            break;

  if(i==-1)
    strcpy(c,"0");
else
 {  n=i;
  for(i=0,j=n;i<j;i++,j--)
  {
       t=cc[i];cc[i]=cc[j];cc[j]=t;
  }

   for(i=0;i<=n;i++)
     c[i]=cc[i]+'0';
  c[i]='';
  }
 }

int main()
{
    char b[1000],a[1000],c[2000];
    while(~scanf("%s%s",a,b))
    {
        bigmul(a,b,c);
        printf("%sn",c);
    }
    return 0;
}