Convert 0 to 1 and Vice Versa

Question

I was asked in an interview : how to convert 0 to 1 and 1 to 0. I answered :

1. Simple if and switch
2. Bit flipping.

Are there any other approach?

Answer 1

Simple arithmetic:

x = 1 - x;

Actually, there are an infinite number of polynomials that will map 1 to 0 and vice versa. For example:

x = x * x * x * x * x - x * x * x * x + x * x - 2 * x + 1;

Answer 2

I guess you could do ABS(VAR - 1) but i think your approaches are more elegant

Answer 3

A few obvious possibilities:

!n
1-n
n^1
n==0
n!=1
n<1

Answer 4

they probably expected you to use bitwise NOT

Answer 5

This should work for any two numbers...

(EDIT: looking at the other answers I may have misread the question... but I still like my answer :-)

public class X
{
    public static void main(final String[] argv)
    {
        int x = Integer.parseInt(argv[0]);
        int y = Integer.parseInt(argv[1]);

        x += y;
        y = x - y;
        x = x - y;

        System.out.println(x);
        System.out.println(y);
    }
}

Answer 6

Lookup table:

int[] swap = { 1, 0 };

And later:

x = swap[x];

Answer 7

This one isn't the best, but it works:

pow(0, n);

Answer 8

Some Trig: COS(PI * N)^2

In python

import math
math.cos(math.pi * n)  ** 2

I can't believe people forgot modulus:

(3 + n) % 2

Answer 9

Take a paper clip. Straighten it out. It's a 1. Bend it to meet its ends. It's a 0. To make it a 1, straighten it.