Handling Large Numbers in C++

In C++, we can use large numbers by using the boost library. This C++ boost library is widely used library. This is used for different sections. It has large domain of applications. For example, using boost, we can use large number like 2⁶⁴ in C++.

Here we will see some examples of boost library. We can use big integer datatype. We can use different datatypes like int128_t, int256_t, int1024_t etc. By using this we can get precision up to 1024 easily.

At first we are multiplying two huge number using boost library.

Example

#include<iostream>
#include <boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
using namespace std;
int128_t large_product(long long n1, long long n2) {
   int128_t ans = (int128_t) n1 * n2;
   return ans;
}
int main() {
   long long num1 = 98745636214564698;
   long long num2 = 7459874565236544789;
   cout << "Product of "<< num1 << " * "<< num2 << " = " <<
   large_product(num1,num2);
}

Output

Product of 98745636214564698 * 7459874565236544789 =
736630060025131838840151335215258722

Another kind of datatype is that Arbitrary Precision Datatype. So we can use any precision using cpp_int datatype. It automatically assigns precision at runtime.

Example

#include<iostream>
#include <boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
using namespace std;
cpp_int large_fact(int num) {
   cpp_int fact = 1;
   for (int i=num; i>1; --i)
      fact *= i;
   return fact;
}
int main() {
   cout << "Factorial of 50: " << large_fact(50) << endl;
}

Output

Factorial of 50:
30414093201713378043612608166064768844377641568960512000000000000