C++ BigInteger

This is a normal implementation of BigInteger for C++, support the operation of much more than 2^64 or 1000 width integer. But please notice that the author@ChiZuo will not take any responsibility for any lost caused by any bugs in this respository. This implementation has a not bad performance in add and sub operations, but low performance in multiply and divide operations between very large numbers compared with BigInteger class in Java11.

Environment

Works well in C++11.

Compiler	OS	Support
GCC-Clang 8.1.0	Windows	pass
MSVC-Clang 8.0.1	Windows	pass
MSVC 10.0	Windows	pass

Function

Support and Finished:

1. comparison ==, !=, <, <=, >, >=
2. add +, ++, +=
3. sub -, --, -=
4. multiply *, *= (Karatsuba Algorithm)
5. divide /, /=
6. mod %, %=
7. power (QuickPower Algorithm)

Unfinished but planned:

1. support BigDecimal

QuickStart

1. clone or download this project
2. include the header file (make sure at the same level as your source code file)

   #include <BigInt.h>
   

3. create BigInt object
   • input long long int

     long long int x = 123456789;
     BigInt temp(x);
     

   • input string object

     string pos_x = "123456789"; //or "+123456789", both means positive number
     BigInt pos_temp(pos_x);
     string neg_x = "-123456789"; //means negative number
     BigInt neg_temp(neg_x);
     

4. operation For example, we want $[(x+1)^2 \times 123 \div y] \mod y$, which $x=-123456789, y=88888888$

   BigInt x("-123456789");
   BigInt y("88888888");
   ++x;
   x = x.power(2);
   x *= 123;
   x /= y;
   x %= y;
   

5. output
   • to string

   BigInt temp("-123456789");
   string temp_str = temp.to_string();
   

   • cout

   BigInt temp("-123456789");
   cout << temp;
   terminal will show: -123456789
   

Reference

My work referenced:

1. Karatsuba in Wiki https://en.wikipedia.org/wiki/Karatsuba_algorithm (this page in zh has wrong in example codes)
2. An implementation of BigInteger for C++ https://github.com/panks/BigInteger

License

Under Apache-2.0 license.