How to swap two numbers without using 3rd variable..?

Question

Suppose x=2 and y=4. How will you make y=2 and x=4 without using any third variable??

Answer 1

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

as x=2 and y=4

x=x+y= 2+4=6

y=x-y= 6-4=2

x=x-y= 6-2=4

you can check it on any input

Answer 2

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

Answer 3

You can also use XOR.
x = x ^ y;
y = y ^ x;
x = x ^ y;

Answer 4

x, y = y, x