大数相乘练习

#include <iostream>
#include <memory>

using namespace std;


int* BigNumberMulti(int arr1[], int length1, int arr2[], int length2)
{
	int len = length1 + length2;
	int* ret = new int[len];
	memset(ret, 0, sizeof(int)*len);

	for (int i = 0; i < length1; i++)
	{
		int x = i;
		for (int j = 0; j < length2; j++)
		{
			ret[x++] += arr1[i] * arr2[j];
		}
	}

	for (int k = 0; k < len-1; k++)
	{
		if (ret[k] > 10)
		{
			ret[k + 1] += ret[k] / 10;
			ret[k] = ret[k] % 10;
		}
	}
	return ret;
}


int main()
{
	int arr1[] = { 1,2,3,4,5,6,7,8,9 };
	int arr2[] = { 9,8,7,6,5,4,3,2,1 };
	int len1 = sizeof(arr1) / sizeof(arr1[0]);
	int len2 = sizeof(arr2) / sizeof(arr2[0]);
	int resultLen = len1 + len2;
	int* result = BigNumberMulti(arr1, len1 , arr2, len2);
	for (int i = resultLen -1; i >= 0; i--)
	{
		cout << result[i] << " " ;
	}
	cout << endl;
	delete[] result;
    return 0;
}