[Design] Two's complement (2's complement)

Overview

Two’s complement is a binary signed number representation.

Negative values are taken by subtracting the number from 2^n. This is the most common method of representing signed integers on computers.

Example

So basically ‘1111 1111’ means -1, and ‘1000 0000’ means -128.

Special case

In java, minimum integer = -2147483648, which is “10000000000000000000000000000000”. If we negative this value, we still get -2147483648!

public void solve(int A) {
    System.out.println(A);
    System.out.println(Integer.toBinaryString(A));
    System.out.println(A * -1);
    System.out.println(Integer.toBinaryString(-1 * A));
    System.out.println(-A);
}

We get:

-2147483648
10000000000000000000000000000000
-2147483648
10000000000000000000000000000000
-2147483648