[c][explained] The XOR Swap

[@MoMadNU]

This swapping problem was assigned to my son over spring break at his university. I have been in the industry 40+ years and was not aware of this method. Even in assembly programming we used a third register as a temp which is more efficient than XOR, and there is no edge case. When my son presented the XOR solution, the professor did not even know that a circumflex is the XOR operator let alone how to use it. I can't wait to see the professor's solution when the assignment explicitly said "without allocating any extra storage" 🤣

[@theteachr]

Post the prof’s solution once they do show it. Although the one below is what I’ve most commonly seen:
a = a + b;
b = a - b;
a = a - b;

[@MoMadNU]

@@theteachr That's exactly what she provided. She failed to mention however that it can cause an overflow or underflow condition

[@artasheschalabyan8490]

Very nice video, it explained things quite clearly in a way that other videos did not

[@EzelBayraktar964]

omg cs 2nd grade student and this... this amazed me. extremely sophisticated work thanks bro

[@arthur.s]

Gorgeous visuals, the part that helped me was realizing that properties apply to propositional operations. I assume distributive property could also work?

[@theteachr]

It doesn’t distribute over addition.
1 ^ (1 + 2) ≠ 1 ^ 1 + 1 ^ 2

[@astrolemonade349]

Awesome video ! What is the name of the monospaced font you used ?

[@theteachr]

Thank you! It's ProFont X.

[@astrolemonade349]

@@theteachr thank you

[@ExplosiveLizard]

Darn that edge case is really bugging me, I can't seem to figure it out... Love your vids btw

[@theteachr]

Stop reading this comment if you are still trying to figure it out on your own.
What is a ^ a?

[@ExplosiveLizard]

@@theteachr a ^ a = 0... but I'm a little confused how this would ruin the data, because a ^ 0 = a so you can still retrieve the number

[@theteachr]

@@ExplosiveLizard What do you think would happen if you call the routine on two different variables that had the same value?

[@ExplosiveLizard]

@@theteachr the result would be 0. But I tried running the code in a variety of languages and the variables stay the same after the executing the expressions

[@thatcrockpot1530]

@@theteachr so in C:
void xorswap(int a, int b) { ... }
(a != b) ? xorswap(a, b) : NULL;
Not ansi compliant btw

[@TechByte8]

Very well explained.

[@senzmaki]

@theteachr I'm so confused like if a and b were 9 like wouldn't this happen
a = 9^9 = 0
b = 9^0 = 9
a = 9^0 = 0
so nothing would change??

[@theteachr]

I need to &my_mistake. Your last swapping line should have been `a = 9 ^ 0 = 9`, by the way.

[@senzmaki]

@@theteachr thanks I don't know how I even made such a simple mistake

[@theteachr]

The point you’re (I did too) missing is that a and b are pointers. When a and b are the same, it means that they’re pointing to the same variable. The first statement will make the variable 0. b in the next statement will also be 0 as it was pointing to the same location.

[@senzmaki]

@@theteachr Ok I see now, thanks

[@IrfanAli-so5hh]

You opened my eyes bro(*´︶`*)♡Thanks!

[@gauravsharma3444]

Well explained 🔥🔥

[@fadiashraf5181]

Thank you !!!
❤❤

[@SANDVlCH]

Isn’t the edge case when a and b are equal?

[@theteachr]

It is.

[@vinyasns]

2nd line should have been b = b ^ a?

[@theteachr]

XOR is commutative. Works fine, unless I'm wrong.

[@vinyasns]

@@theteachr right, my bad