模闆——大數相乘

兩個大數相乘

# include<stdio.h>
# include<string.h>
# include<algorithm>
using namespace std;

char a[300],b[300];
int main()
{
	while(scanf("%s%s",a,b)!=EOF)
	{
		  if(a[0]=='0'||b[0]=='0')
		  {
			  printf("0\n");
			  continue;
		  }
		  int length_a=strlen(a);
		  int length_b=strlen(b);
		  reverse(a,a+length_a);
		  reverse(b,b+length_b);
		  int ans[600];
		  memset(ans,0,sizeof(ans));
		  for(int i=0;i<length_a;i++)
		  {
			  int temp[600],s,c=0;
			  memset(temp,0,sizeof(temp));
			  for(int j=0;j<length_b;j++)
			  {
				  s=(a[i]-48)*(b[j]-48)+c;
				  temp[j+i]=s%10;
				  c=s/10;
			  }
			  int cycle=0;
			  while(c!=0)
			  {
				    temp[cycle+i+length_b]=c%10;
					c/=10;
					cycle++;
			  }
			  c=0;
			  for(int k=0;k<600;k++)	
			  {
				  s=temp[k]+ans[k]+c;
				  ans[k]=s%10;
				  c=s/10;
			  }
		  }
		  int sign;
		  for(int i=599;i>=0;i--)
		  {
			  if(ans[i])	
			  {
				  sign=i;
				  break;
			  }
		  }
		  for(int i=sign;i>=0;i--)		printf("%d",ans[i]);
		  printf("\n");
	}
	return 0;
}