大数乘法

void multiply()
{
	char str1[1000],str2[1000];
	cin>>str1>>str2;
	int len1 = strlen(str1);
	int len2 = strlen(str2);
	int len = len1 + len2 + 1;
	int *A = new int[len1];
	int *B = new int[len2];
	int *C = new int[len];
	for(int i=0;i<len1;i++)
		A[i] = str1[len1-i-1]-'0';
	for(int i=0;i<len2;i++)
		B[i] = str2[len2-i-1]-'0';
	for(int i=0;i<len;i++)
		C[i] = 0;
	bool flag = false;
	for(int i=0;i<len1;i++)
		for(int j=0;j<len2;j++)
			C[i+j] += A[i] * B[j];
	for(int i=0;i<len;i++)
	{
		if(C[i]>9)
		{
			C[i+1] += C[i]/10;
			C[i] %= 10;
		}
	}

	for(int i = len-1; i>=0;i--)
		if(flag)
			cout<<C[i];
		else if(C[i]!=0)
		{
			cout<<C[i];
			flag = true;
		}
	delete []A;
	delete []B;
	delete []C;
}