Declare a Big Integer in C++ [duplicate] - c++

Question

This question already has answers here:
STL BigInt class implementation
(3 answers)
Closed 7 years ago.
I am trying to run this algorithm in c++ in order to get a big number
#include<iostream>
using namespace std;
int main()
{
int num,factorial=1;
cout<<" Enter Number To Find Its Factorial: ";
cin>>num;
for(int a=1;a<=num;a++)
{
factorial=factorial*a;
}
cout<<"Factorial of Given Number is ="<<factorial<<endl;
return 0;
}
How can I declare a Big Integer like in Java instead of an int?

Answer 1

There is no big-integer support in the C++ standard library. A common choice for big-number arithmetic is GMP. After downloading and installing the library, in your code you would #include <gmpxx.h> and declare mpz_class factorial instead of int factorial, then link against GMP.
Linking with GMP can be done in an IDE, by adding GMP in your editor’s compile settings; or by adding -lgmp to your compilation command (e.g., g++ or clang++).

Answer 2

There is no arbitrary-precision arithmetic in c++ standard library. You'll need to implement it yourself using an array of integers, or use an existing non-standard library.

Answer 3

Try unsigned long long int for just convenience.
I just want to leave it as comment but I have low repu for commenting..

Answer 4

There is no standard support for arbitrary-precision integers. However, a few libraries are available for handling big integers:
GNU MP Bignum Library
InfInt
C++ BigInt class
BigDigits multiple-precision arithmetic (in C)
BigIntegerCPP (only supports addition and multiplication)
C++ Big Integer Library (no longer maintained)