One way to solve this problem is to make a linked list (u can use a vector
as well, but i used array when i was solving this problem) of digits that
form a number class. This would look something like this:
public digit {
private:
int _digit;
int *next;
...
};
public number {
private:
int *digit;
...
public:
multiply(number n)
{
...
}
}
This is one way to solve this problem ... however, u can optimize it.
On Sun, Aug 14, 2011 at 4:10 AM, Bartholomew Furrow <[email protected]>wrote:
> Mandy,
>
> One thing I'm not sure has been made clear is *why* you're getting an
> error.
>
> In C++, numbers can be stored in a few different ways. It sounds to me
> like you're using an *int*, which can usually correctly store integers
> between about -2 billion and +2 billion.
>
> What happens when you try to store a number more than 2 billion? Your
> program doesn't fail, but it instead does something that might seem strange.
> Write a program like the following:
>
> int x = 2147483647; // The highest number an int can represent
> cout << x << endl;
> x = x + 1;
> cout << x << endl;
>
> Your program will probably output -2147483648. That's because in C++,
> your first number was stored, in binary, as a 32-bit number:
> 01111111111111111111111111111111
> Then when you added 1 to it, you got:
> 10000000000000000000000000000000
>
> ...which is how C++ represents -2147483648 using its two's
> complement<http://en.wikipedia.org/wiki/Two's_complement#Two.27s-complement_numbers>notation.
> If you were to keep adding one, you'd eventually get to:
> 11111111111111111111111111111111
> ...which is how C++ represents -1. Add one to that, and you get:
> 00000000000000000000000000000000
> ...which is how C++ represents 0. Notice that in binary, if you added 1 to
> that number, it would normally start with a 1:
> 100000000000000000000000000000000
> ...but C++ only uses 32 bits to store an integer, so it drops the 33rd.
>
> So what you're seeing is an error that comes from the fact that C++ can't
> store a number bigger than about 2 billion in an int. Instead of an int you
> can use a *long long*, which can store larger numbers (up to about 9
> billion billion, using 64 bits), but that will only get you up to 20
> factorial. Look at some of the excellent suggestions in this thread for how
> to store numbers larger than that. As Luke pointed out, for example, the
> language Python will automatically use more bits when it needs to; or you
> could write a library in C++ that would let you use more bits.
>
> Best,
> Bartholomew
>
> P.S. If you look carefully, you'll probably see your program only
> calculated up to 13 factorial correctly. The number it computes for 14
> factorial is actually *smaller*, because C++ couldn't store the larger
> number, and so it dropped all the bits after the 32nd bit. This is called
> "overflow". Once you get to 17!, you'll see that you got a negative number,
> because bit #32 happened to be 1.
>
> On Wed, Aug 3, 2011 at 1:19 AM, mandy <[email protected]> wrote:
>
>> Can anyone tell me how to compute factorial of 50 in c++ and even for
>> bigger no.
>> I am getting error(a default value)
>>
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