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Don't think you can brute force part 2... so a little thinking beforehand.
If you want the inner trick for part 2:
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
I think you can brute force if you reduce the problem on every iteration
Here is my iterative macro
Full solution at https://gitlab.com/adriley/adventofcode2020-alteryx/-/blob/master/day10-part2.yxmd
Struggled with Part 2, and found help on the adventofcode subreddit. Immediately tried to brute force it until I noticed the 'trillions'
workflow
Part 1 iterative
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.
I tried to make all pattern, but it was failed.
And then, I try to calculate combination numbers.
As anonymous user #1105310
Revisited part 2 after some reddit research and the hint from @jdunkerly
-- A nice explainer here https://www.reddit.com/r/adventofcode/comments/ka9pc3/2020_day_10_part_2_suspicious_factorisation/
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.
Day 10 part A felt more like a day 1 question.
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.
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.
