data comparision issue

Hello guys,

I just encountered an issue with data comparison; I managed to sort out the problem. However, just out of my curiosity, I would like to find out why it doesn’t work with my A solution. ( the B solution works! )

My question is :

There are 102 objects at 12 different heights in total. ( the order of the data at each height doesnt matter at this point. ) All I would like to do is to separate the list of data into different branches based on its z value as shown on the image. It somehow just doesn’t work when I subtracted two sets of data. ( aiming to get a 0 value when they are at the same height. ) However, when I replaced the number I would like to search into 1 in the list, then do the same operation by checking if the numbers in the set of data equal to 1, then I got it worked.

Does anyone know why? Very appreciated for the answer! Thanks!

Best,

Nicholas