Originally Posted by unleashed-my-freedom
We use temp because otherwise you would loose a value. Think like you have two cups (A and B) in two positions (1 and 2 respectively) that each of them can place only one
cup and you can carry only one cup in your hands. Now, if you want to exchange positions between cups you start like this:
take cup A and put it in position 1. But then you have to throw away cup B(because you can't have two cups in you a position or in your hands).
Therefore you need a new assisting position (3).
Then you put
1) cup A to position 3 - now position 1 is empty
2) cup B to position 1 - now position 2 is empty
3) cup A to position 2
is the assisting position.
Hope that makes sense.