this post was submitted on 19 Jun 2023
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Python

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[Meme] Swapping integers in Python (lemmy.world)
submitted 1 year ago* (last edited 1 year ago) by jnovinger@programming.dev to c/python@programming.dev
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Yay or nay, memes should be allowed in !python@programming.dev ?

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[–] ActuallyRuben@actuallyruben.nl 3 points 1 year ago (3 children) 
a ^= b
b ^= a
a ^= b
[–] Hammerheart@programming.dev 1 points 1 year ago (2 children)

I'm gonna need you to elaborate on this one

[–] dmad@programming.dev 5 points 1 year ago* (last edited 1 year ago) (1 children)

xor has the property x ^ x = 0, and x ^ 0 = x. So, x ^ x ^ y = y

a' = a ^ b
b' = b ^ a' = b ^ (a ^ b) = a
a'' = (a ^ b) ^ a = b

This is pretty clever, I've never seen this for a swap.

[–] ActuallyRuben@actuallyruben.nl 2 points 1 year ago

Couldn't have explained it better myself. I don't remember where exactly I first read about this trick, but it's mainly useful in C or Assembly, as you don't have to resort to using a third variable/register.