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this post was submitted on 02 Dec 2024
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Re: day 7 parts 1 and 2
same here, I was dicking around with combinatorics to get all combos of plus and multiply but realized before I got to the end it was gonna take too long. Then I figured that a DFS was the way to go.
I tried to optimize a bit by exiting early if the cumulative result became too large, but for some reason that gave me incorrect (too low) answers. Part 2 runs in around 1 min anyway.
https://github.com/gustafe/aoc2024/blob/main/d07-Bridge-Repair.pl
My graph search solves 7-1 and passes the example cases for 7-2, but gives too low a result for the complete puzzle input, and there's no way I'm manually going through every case to find the false negative. On to day 8 I guess.
7-2 Check case by simple graph search that mostly works
EDIT: total && index < (calibration.Length-1) -> false -- i.e. stop if you reach the total before using all numbers, well, also stops you from checking the next operator, So, removing it worked.
Rubber ducking innocent people on the internets works, who knew.
this looks like the same issue I had!
re: branch cutting
IDK if this is what your issue was, but one thing I ran into was that if you do something likeif (current_total >= target) prune(),
this can be problematic because if the tail end of the data is 0s and 1s, you exit too early. Basically I would prune strictly when the current total > target.re: branch cutting
thanks for the tip, I looked into it again and I found I was cutting in the wrong place. Fixed now, and halves the time for part 2
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