大数相乘练习

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#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; }