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BigInt (Big Integers) in C++ with Examples

The C++ big integers (BigInts) refer to the ability to work with integers that are larger than the typical built-in integer types like int or long long. You can achieve this using libraries or classes that provide arbitrary-precision arithmetic. One popular library for working with big integers in C++ is the GNU Multiple Precision Arithmetic Library (GMP). Here, I’ll provide an example of using GMP to work with BigInts.

Example of Using GMP for BigInts:

First, you need to install the GMP library and its development headers. On many Linux distributions, you can use the package manager to install it:

Bash
sudo apt-get install libgmp-dev  # On Debian/Ubuntu

Now, you can write C++ code using GMP:

C++
#include <iostream>
#include <gmpxx.h>

int main() {
    // Declare BigInt variables
    mpz_class bigInt1, bigInt2, result;

    // Initialize BigInts with values
    bigInt1 = "123456789012345678901234567890";
    bigInt2 = "987654321098765432109876543210";

    // Perform arithmetic operations
    result = bigInt1 + bigInt2;

    // Output BigInt result
    std::cout << "Sum: " << result << std::endl;

    return 0;
}

In this example:

  • We include the <gmpxx.h> header to use GMP’s C++ interface.
  • We declare BigInt variables using mpz_class.
  • We initialize BigInts with values using string literals. GMP automatically handles the conversion from strings to BigInts, allowing you to work with arbitrarily large integers.
  • We perform arithmetic operations (in this case, addition) on BigInts just like you would with built-in integer types.
  • We print the result using std::cout.

Compile this code with the -lgmpxx -lgmp flags to link against the GMP library:

Bash
g++ -o bigIntExample bigIntExample.cpp -lgmpxx -lgmp

When you run the executable, you’ll see that GMP handles large integers without loss of precision.

Keep in mind that GMP provides a wide range of functions for arithmetic operations, number theory, and more. You can refer to the GMP documentation for details on how to use these functions effectively: https://gmplib.org/manual/.

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