Advent of Code 2024
adventofcode.com

copy pasting the rules from last year’s thread:

Rules: no spoilers.

The other rules are made up aswe go along.

Share code by link to a forge, home page, pastebin (Eric Wastl has one here) or code section in a comment.

  • gerikson@awful.systemsEnglish
    2·
    21 days ago
    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

    • Architeuthis@awful.systemsOPEnglish
      3·
      20 days ago

      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 
      // F#
let isLegit ((total: int64), (calibration : int64 array)) = 

    let rec search (index : int) (acc: int64) =
        let currentValue = calibration.[index]
        
        [Add; Times; Concat] // operators - remove 'Concat' to solve for 7-1
        |> List.exists (fun op -> // List.exists returns true the first time the lambda returns true, so search stops at first true
                match op with // update accumulator
                | Add -> acc + currentValue
                | Times -> acc * currentValue
                | Concat -> int64 (sprintf "%d%d" acc currentValue)
                |> function // stop search on current accumulator value (state) exceeding total, or being just right
                | state when state > total -> false
                | state when state = total && index < (calibration.Length-1) -> false // this was the problem
                | state when state = total && index = (calibration.Length-1) -> true
                | state -> // stop if index exceeds input length, or continue search
                    if index+1 = calibration.Length
                    then false
                    else search (index+1) state
        )
     
    // start search from second element using the first as current sum
    search 1 calibration.[0]

      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.