A1023 Have Fun with Numbers (20) 大整数的四则运算

这个的解法很清晰，但是实在是太长了，后面会优化或者采用更加简洁的写法的

#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;
int r=0;
struct bign
{
	int d[1000];
	int len;
	bign()
	{
		memset(d,0,sizeof(d));
		len=0;
	}
};
bign change(char s[])
{
	bign a;
	a.len=strlen(s);
	for (int i=0;i<a.len;i++)
	{
		a.d[i]=s[a.len-i-1]-'0';
	}
	return a;
}
void print(bign a)
{
	for (int i=a.len-1;i>=0;i--)
	{
		printf("%d",a.d[i]);
	}
}
bign multi(bign a)
{
	bign c;
	int carry=0;
	for (int i=0;i<a.len;i++)
	{
	  carry=a.d[i]*2+carry;
	  c.d[c.len++]=carry%10;
	  carry=carry/10;	  
	}
	while (carry!=0)
	{
		c.d[c.len++]=carry%10;
		carry/=10;
	}
	return c;
}
int main()
{
	char s[1000];
	scanf("%s",s);
	bign a=change(s);
	int hashtable[10]={0};
	for (int i=0;i<a.len;i++)
	{
		hashtable[a.d[i]]++;
	}
	bign b=multi(a);
	if(b.len!=a.len)
	{
		printf("No\n");
	}
	else
	{
	int i;
	for ( i=0;i<a.len;i++)
	{
		if(hashtable[b.d[i]]!=0)
		{
			hashtable[b.d[i]]--;
		}
		else
		{
			printf("No\n");
			break;
		}
	}
	if(i==a.len)
	printf("Yes\n");
    }
    print(b);
}