大数乘法

#include<cstring>

using namespace std;

class MData

{

 private:

    int n,m;

    char *str1,*str2;

 public:

    char *GetSum();

    MData();

    MData(const char *s1,const char * s2);

    void init(const char *s1,const char * s2);

    ~MData();

};

MData::MData()

{

    str1=nullptr;

    str2 = nullptr;

    n = 0;

    m = 0;

}

MData::MData(const char *s1, const char *s2)

{

    n = (int)strlen(s1);

    m = (int)strlen(s2);

    str1 = new char[n+1]{''};

    str2 = new char[m+1]{''};

    strcpy(this->str1,s1);

    strcpy(this->str2,s2);

}

void MData::init(const char *s1,s2);

}

MData::~MData()

{

    if(str1!=nullptr)

        delete[] str1;

    if(str2!=nullptr)

        delete[] str2;

}

char* MData::GetSum()

{

    //cout<<str1<<endl<<str2<<endl<<n<<endl<<m<<endl;

    int *s = new int[n+m];

    for(int i = 0;i<n+m;i++)

    {

        s[i] = 0;

    }

    for(int i = 0;i<n;i++)

        for(int k = 0;k<m;k++)

        {

            s[i+k+1] += (str1[i]-'0')*(str2[k]-'0');

        }

//    for(int i = 0;i<n+m;i++)

//    {

//        cout<<s[i]<<endl;

//    }

    for(int i = n+m-1;i>=0;i--)

    {

        if(s[i]>=10)

        {

            s[i-1] += s[i]/10;

            s[i] %= 10;

        }

    }

    int i = 0;

    while(s[i] == 0)

    {

        i++;

    }

    char *sum = new char[n+m-i+1]{''};

    int k = 0;

    int kn = n+m-i+1;

    for(;k<kn&&i<n+m;k++,i++)

    {

        sum[k] = s[i]+'0';

    }

    sum[k] = '';

    delete[] s;

    return sum;

}

int main()

{

    char *str1=new char[100]{''},*str2=new char[100]{''};

    cin>>str1;

    cin>>str2;

    MData sk(str1,str2);

    char *fk = sk.GetSum();

    cout << fk << endl;

    delete[]str1;

    delete[]str2;

    return 0;

}