Swapping two variables in Java without using a third variable or an API

Question

I recently went to an interview and I was asked to write some code to swap the values of two variables without using third variable or any API.

I could not work out how to do this, can you help me on this?

For example I have two variable a=10 and b=20 the output should be b=10 and a=20.

score 1 · Answer 1 · answered Mar 10 '14 at 19:23

1

Tricky but not that hard to figure out:

a = 10
b = 20

a = a + b; //a = 30, b = 20
b = a - b; //a = 30, b = 10 
a = a - b; //a = 20, b = 10

answered Mar 10 '14 at 19:23

Nima

adding 10 and 20 causes overflow? – Nima Mar 10 '14 at 19:25
Do we have any algorithm to swap.Here we are going with values.Suppose if we have to read the values from the keyboard and the with the swapped output mean how to solve @Nima – user3351552 Mar 10 '14 at 19:42
If instead of 20 you use Integer.MAX_VALUE you will get overflow. However, I think it all comes out in the wash and the values should be correct at the end. – Richard Miskin Mar 10 '14 at 20:05
this doesn't work with strings.. use XOR algorithmn as mentioned above – PolishDeveloper Mar 10 '14 at 20:09
@PiotrMiazga XOR swap won't work for String either. – Radiodef Mar 10 '14 at 20:10
@Nima then how in the case of String??? – user3351552 Mar 10 '14 at 20:29

1 Answers1