Advent of Code 2024 Day 8 (BaseA Style)

[AlteryxCommunityTeam]

Discussion thread for day 8 of the Advent of Code - https://adventofcode.com/2024/day/8

[CoG]

Eric is treating us right for the weekend! Very refreshing (Scored top 1000 for both parts today). Reading the problem felt harder than solving it:

Spoiler

Brute force all the way. Small map size makes this problem trivial to solve!

[ScottLewis]

A second straightforward day in a row. Probably too much to hope for one more in advance of Monday Morning Meetings but we'll find out in 24 hours.

This marks the only time I've ever been happy that joins are case sensitive.

Spoiler

This is pretty much an intermediate data tricks lesson. Filter out junk, join with yourself to generate all possible combinations, throw out self joins, calculate the two antinodes from the two points (or the 50 possible for part 2) for each pair, unique the thing and count the rows. Bing. I missed that the possible count is N, rather than N/2 for part 2, which kept me out of the rarified triple digit air but otherwise this is a very good one for Alteryx.

[gawa]

Difficult part was to understand what we are asked to do rather than configuring WF today.

I might have violated Base-A...I used a pencil and paper. I love @CoG 's neat and wise WF. It's elegant.

Spoiler

Part1: Create all pair of the same antennas, and  calc X-Y of antinodes at opposite side. Once understanding the concept, it's not difficult.
Part2: I used linear algebra; Y = aX + b. By using intermediate result of part1, we can find two parameters 'a' and 'b' easily by the Formula tool. Cross join all of lines and points, and check points are on it. As 'a' and/or 'b' can be decimal, result of expression 'Y - (aX + b)' is not always exactly equal to 0 (0.0001234 etc). I applied fuzzy threshold like ABS([Y]-([a]*[X]+[b])) < 0.01, and it worked well in this case.

 (Edit) For part2, if linear algebra method is applied, it's successful because of:

I was just luck to have solved it without knowing this nature of data.

Spoiler

Span-X and Span-Y is relatively prime(互いに素) for any pair of antenna. Line between two antenna does not intersect any points within that range. 
That means the extended line outside of two antenna will Intersect points where they locate at multiple of Span-X/Y, that are we are asked to find.

[DataNath]

Wow - didn't expect this after some of the challenges we've had this week! Did almost have an absolute meltdown trying to parse the question originally though. Finished ~5k for both parts on the global leaderboard which is pretty sweet. Went overboard generating rows for P2 but hey ho, covering bases = stars apparently.

Spoiler

  

[kelsey_kincaid]

I'm sure someday I'll feel confident with grid problems, but I won't get there without practice! I spent a decent amount of time trying a spatial solution, but I didn't get very far with that.

I'm 100% sure I overcomplicated this one, but I was happy that Part 2 didn't take toooo long to get to from Part 1. 

Spoiler

I nested iterative macros within a batch macro, which is why I'm certain I overcomplicated it, but it still runs quickly which is nice. 

Batch Macro: 
All this is doing is filtering down to antennae that have the same transmission value. I used REGEX_Match with case sensitivity to ensure the difference between 'a' and 'A' would be captured here.

Iterative Macro(s):
My part 1 and part 2 macros are identical except for the Generate Rows tool & a small tweak to the formulas.
I take each row of data and join it with every other row of data that has the same transmission value. Then it computes the location of each antinode.

The generate rows tool for Part 2 provides a multiplier. This lets me compute all of the points along the line that could possibly be within the specified size of grid. 

EDIT: Seeing the other (much simpler) solutions is a good lesson for me. Sometimes my mind jumps straight to macros for AoC and it doesn't need to! 

[Yoshiro_Fujimori]

For Part 2, at first I tried "Generate Rows" or "Append Fields".

As it did not seem to work well, I switched to Iterative Macro and it worked.

Spoiler

Workflow

Macro for Part2

[DaisukeTsuchiya]

Done. I can sleep tonight.

Spoiler

[AkimasaKajitani]

Solved!

 

Not elegant, but work!

Spoiler

I was able to use the Arrange tool to stack multiple x,y elements vertically!

[mmontgomery]

Day8. More in spoiler

Spoiler

P1: Spent most of the time drawing the relationships by hand and then creating the formulas around the hand calcs to make it easier to see
P2: Take P1 framework but apply it to generate rows while setting boundaries relative to the map size