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Variable Switch

Logic puzzles require you to think. You will have to be logical in your reasoning.

 

Puzzle ID:#49422
Fun:** (1.94)
Difficulty:*** (2.31)
Category:Logic
Submitted By:rob77*ca*****!

 

 

 



You're a computer programmer, and the program you're writing has numeric variables A and B. You need the computer to switch the variables so that the number in variable A becomes variable B, and the number in variable B becomes variable A. Adding a third variable would use more memory though, so how can you do that switch without using another variable? Use commands such as B=B-A to assign a new value to B.



Answer

B = A+B
A = B-A
B = B-A

Using an example, if A=5 and B=4:
B = 5+4
A = 9-5
B = 9-4
A is now 4 and B is now 5.

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Comments

royale-ninja
Jul 24, 2012

i got it...i solved it by another answer
A=B-A
B=B-A
A=A+B
royale-ninja
Jul 24, 2012

i got it...i solved it by another answer
A=B-A
B=B-A
A=A+B
edoridlo
Oct 14, 2013

How about this way?
A = A + B
B = A - B
A = A - B
rob77*ca*
Jan 08, 2014

This was a real exercise I got in a course.
Dezaxa
Dec 29, 2014

The smart alec answer is to emply some assembler and use registers, e.g.
load location of A to register X
load location of B to register Y
save X to location of B
save Y to location of A

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