Computer related puzzles and questions

[DominO123]

sebastia...

 

Sip's answer to that will be that he met "one"-- at office depot -- but it didnt have a good/reliable hard drive---

 

if u dotn get it...just forget it- im not making sense anymore....

To the contrary dear, I think you are making more sense than ever.

[Harut]

You have 2 integers A and B

 

How do you swap their values without using any temporary variables.

permanent = A

A = B

B = permanent

 

j/k

[Twilight Bark]

I am not sure if Sipchik or anyone else has asked this question. Most likely they have. But I will give it another try today.

 

You have 2 integers A and B

 

How do you swap their values without using any temporary variables.

A = A + B

B = A - B

A = A - B

[Sasun]

A = A + B

B = A - B

A = A - B

that's the coolest thing I have seen lately

[Sip]

TB is obviously thinking like a mathematician!

 

The more computery dude would probably come up with

 

A = A xor B

B = A xor B

A = A xor B

 

In C/C++ or Java, you can even write it as

 

A ^= B ^= A ^= B;

 

 

Conceptually there is really no difference between the arithmetic version and the logical version but as it turns out, this one can be made much faster in hardware. Also, in the strict "binary" bit-wise sense of the contents of A and B, the XOR method will swap the bits while the arithmetic version requires some notion of what addition and subtraction mean. It clearly works for integers.