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# General Discussions

Discuss any topics that are not product-specific here.

## Advent of Code 2020 - BaseA Style (Day 10)

16 - Nebula

Discussion thread for day 10 of the Advent of Code : https://adventofcode.com/2020/day/10

24 REPLIES 24
9 - Comet

Well that made my head hurt, drew a few diagrams on paper and tried a few bits out in alteryx but no dice for part 2. Keen to see how it was possible!

ACE Emeritus

Don't think you can brute force part 2... so a little thinking beforehand.

Spoiler

If you want the inner trick for part 2:

Spoiler
A block with steps 113 can have the first 1 removed => so 2 possibilities
A block with steps 1113 can have the first 1, second 1 or both removed => so 4 possibilities
A block with steps 11113 can have first, second, third, first & second, first & third or second & third removed => so 7 possibilities

My data set had no 111113 but think would be 13 possibilities

You can then product these possibilities together to get the total number of possibilities
9 - Comet

Genius! I got stuck somewhere in the middle of identifying optional steps, and calculating how many valid next steps each individual step had, but got lost as to how to bring all of that together.

Alteryx

I think you can brute force if you reduce the problem on every iteration

Here is my iterative macro

Spoiler

Adam Riley
Principal Software Engineer
Tech Lead Core Engines, Alteryx
15 - Aurora

Struggled with Part 2, and found help on the adventofcode subreddit. Immediately tried to brute force it until I noticed the 'trillions'

Spoiler
workflowPart 1 iterative
16 - Nebula

Day 10!

Part1 was very easy. But Part 2 is.... I couldn't have Iterative approach.
My approach is calculating Combination Numbers. It is similar to @OllieClarke 's approach.

Spoiler

I tried to make all pattern, but it was failed.
And then, I try to calculate combination numbers.

As anonymous user #1105310

9 - Comet

Revisited part 2 after some reddit research and the hint from @jdunkerly

Spoiler

Still feels a little shonky though as it wouldn't automatically handle longer chains of 1's up to a 3.
I went through a few different approaches in the disabled container but got lost until seeking help on the maths/logic.

17 - Castor
Spoiler
I went for a lot of multi-row formula tools...

13 - Pulsar

Day 10 part A felt more like a day 1 question.

Spoiler

Still working on Part 2, I am currently stuck down a rabbit hole of thinking there is a brute force binary solution to it by trying to generate a series of 1,0s between record 1 and 104 to act as a T|F flag and then to run my multi row. However that's too big, so trying to slim it down by spotting patterns, for example I know my start and end are fixed. and there are repeating 1,1,3 and 1,1,1,3s and know from experience with some of the previous AoCs now looking for patterns.

Finally got there with the second part.

Spoiler

Took the idea of finding the patterns using regexcountmatch and then unwinding the fact that 3,1,1 appears in 3,1,1,1. It did mean to get the right answer I needed to hard code for sole 1,1 which occurs at the start of my workflow.

Chris
Check out my collaboration with fellow ACE Joshua Burkhow at AlterTricks.com
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