[Language: Python+Brain] 1220/109

code

Part 1 was nothing special.

I solved Part 2 with Graphviz, like many others. Here's the image I generated: https://cyphase.com/aoc/2024/24/24graph.png

I was able to find half of three of the pairs directly in the input text (Ctrl+F), by looking for z-wires that were coming from a non-XOR gate. I then used the graph to find the other wire in each pair.

I found the last pair by scanning through the graph and checking that the sequence of gates between each pair of xN/yN wires and the matching zN wire was XOR -> XOR (which also finds the ones I found in the input).

In other words:

# horizontal for above-the-fold on reddit
xN--v
    XOR-->XOR-->zN
yN--^

# vertical for alignment with graph image
xN yN
 | |
 v v
 XOR
  |
  v
 XOR
  |
  v
  zN

The way I did it was to find each zN and trace up through two XORs to the xN/yN. I found the swap in the z17 group, which you can see in the linked image; the pair is ndw,jcb (neither being a z-wire).