实现bigint计算器c ++ [英] implementing a bigint calculator c++

问题描述

到目前为止，我有一个add，subtract和print函数以及一个初始化为数组的构造函数。由于某种原因，操作（+和 - ）对我来说很有意义（我认为）所以我有点超越自我并且不太确定如何初始化一个大整数，我可以得到一些函数这样的帮助作为void assign（const bigint& A）或类似的东西？如果我的代码有问题，请告诉我。谢谢

So far I've got an add, subtract and print function as well as a constructor that initializes to zero the array. For some reason the operations(+ and -) made alot of sense to me(i think) so I kind of got ahead of my self and am not too sure how to initialize a big integer, could I get some help with a function such as void assign(const bigint & A) or something like that? Also if there is something already wrong with my code please tell me. Thanks

const int size=30;   //just to make things easier, will change to something big later
class bigint
{
    int digits[size];


public:
    // initializes to zero
    bigint()
    {
        for (int i = 0; i < size; i++)
            digits[i] = 0;

    }

    // prints a big int
    void print()
    {
        bigint B;
        for (int i = size - 1; i >= 0; i--)
        {
            int dig = B.digits[i];
            if (dig != 0)
                std::cout << dig;
        }
    }

    // subtracts a bigint(B) from another(A)
    void subtract(bigint & A, bigint & B)
    {
        for (int i = 0, borrow = 0; i < size; i++)
        {
            if (borrow = ((A.digits[i] -= B.digits[i] + borrow) < 0))
            {
                A.digits[i] += 10;
            }
        }
    }

    // adds a bigint(A) to another(B)
    void add(bigint & A, bigint & B)
    {
        for (int i = 0, carry = 0; i < size; i++)
        {
            if (carry = ((A.digits[i] += B.digits[i] + carry) < 9))
            {
                A.digits[i] -= 10;
            }
        }
    }
};

推荐答案

是的，有一个你的班级出了几个问题。



（a）打印功能打印一个新创建的变量B的值，它始终为零。只需使用您自己的会员数字！另外：您的打印功能包含一个错误：它只打印非零数字！



（b）加减成员函数不会触及您的成员数字根本没有意义。相反，您可能希望提供诸如

Yes, there are a couple of things wrong with your class.

(a) The print function prints the value of a newly created variable B, which will be zero all the time. Just use your own member digits instead! Also: Your print functions contains a bug: It just prints the non-zero digits!

(b) The add and subtract member functions don't touch your member digits at all, which doesn't make sense. Instead you might want to provide functions like

void add (const bigint& A);
void subtract (const bigint& A);

向应用操作的对象添加/减去A.



（c）以十进制数字工作不会获得最佳性能并且浪费内存。为什么不在base 2中工作，因此使用内置的算术运算。这将使您的功能性能提高一到两个数量级。只是为了打印一个数字，它需要转换回十进制。

which add/subtract A to/from the object the operation is applied to.

(c) Working in decimal digits will not get you the best performance and is a waste of memory. Why don't you work in base 2 and hence use the built-in arithmetic operations. That will increase the performance of your functions by one or two orders of magnitude. Just for the purpose of printing a number it needs to be converted back to decimal.

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