大数（乘除法）

大数乘法：

string s1,s2;int check(int *a,int n)////去掉前导0 并且调整进位{    int i,len=n;    while(!a[len-1] && len>1) len--;    for(i=0; i<len; i++)    {        if(a[i]>=10)        {            a[i+1]=a[i+1]+a[i]/10;            a[i]=a[i]%10;        }    }    if(a[i]) len=i+1;    return len;}string Int2Str(int *a,int n)///int to string {    int i;    string str("");    for(i=0; i<n; i++) str+=(a[n-i-1]+'0');    return str;}int *Str2Int(string s)////string to int{    int len=s.size();    int *a=new int[(len+1)*sizeof(int)];    for(int i=0; i<len; i++) a[i]=s[i]-'0';    return a;}string mult(string s1,string s2)///乘法运算{    reverse(s1.begin(),s1.end());    reverse(s2.begin(),s2.end());    int len1=s1.size(),len2=s2.size();    int len=len1+len2;    int* t1=new int[(len1+1)*sizeof(int)];    int* t2=new int[(len2+1)*sizeof(int)];    int* ans=new int[(len+1)*sizeof(int)];    t1=Str2Int(s1),t2=Str2Int(s2);    for(int i=0; i<len+1; i++) ans[i]=0;    for(int i=0; i<len1; i++)        for(int j=0; j<len2; j++)            ans[i+j]=ans[i+j]+t1[i]*t2[j];    len=check(ans,len);    return Int2Str(ans,len);}int main(){    cin>>s1>>s2;    cout<<mult(s1,s2)<<endl;    return 0;}

大数除法：