Advent Of Code

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An unofficial home for the advent of code community on programming.dev!

Advent of Code is an annual Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like.

AoC 2023

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❄️ - 2023 DAY 3 SOLUTIONS -❄️ (programming.dev)

submitted 11 months ago* (last edited 11 months ago) by Ategon@programming.dev to c/advent_of_code@programming.dev

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Day 3: Gear Ratios

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[–] Andy@programming.dev 2 points 11 months ago* (last edited 11 months ago)

Factor on github (with comments and imports):

: symbol-indices ( line -- seq )
  [ ".0123456789" member? not ] find-all [ first ] map
;

: num-spans ( line -- seq )
  >array [ over digit? [ nip ] [ 2drop f ] if ] map-index
  { f } split harvest
  [ [ first ] [ last ] bi 2array ] map
;

: adjacent? ( num-span symbol-indices -- ? )
  swap [ first 1 - ] [ last 1 + ] bi [a,b]
  '[ _ interval-contains? ] any?
;

: part-numbers ( line nearby-symbol-indices -- seq )
  [ dup num-spans ] dip
  '[ _ adjacent? ] filter
  swap '[ first2 1 + _ subseq string>number ] map
;

: part1 ( -- )
  "vocab:aoc-2023/day03/input.txt" utf8 file-lines
  [ [ symbol-indices ] map ] keep
  [
    pick swap [ 1 - ?nth-of ] [ nth-of ] [ 1 + ?nth-of ] 2tri
    3append part-numbers sum
  ] map-index sum nip .
;

: star-indices ( line -- seq )
  [ CHAR: * = ] find-all [ first ] map
;

: gears ( line prev-line next-line -- seq-of-pairs )
  pick star-indices
  [ 1array '[ _ part-numbers ] [ 3dup ] dip tri@ 3append ]
  [ length 2 = ] map-filter [ 3drop ] dip
;

: part2 ( -- )
  "vocab:aoc-2023/day03/input.txt" utf8 file-lines
  dup [
    pick swap [ 1 - ?nth-of ] [ 1 + ?nth-of ] 2bi
    gears [ product ] map-sum
  ] map-index sum nip .
;