Day 4: Ceres Search

Megathread guidelines

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FAQ

  • Andy@programming.dev
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    5 days ago

    Factor

    spoiler
    : get-input ( -- rows )
      "vocab:aoc-2024/04/input.txt" utf8 file-lines ;
    
    : verticals ( rows -- lines )
      [ dimension last [0..b) ] keep cols ;
    
    : slash-origins ( rows -- coords )
      dimension
      [ first [0..b) [ 0 2array ] map ] [
        first2 [ 1 - ] [ 1 (a..b] ] bi*
        [ 2array ] with map
      ] bi append ;
    
    : backslash-origins ( rows -- coords )
      dimension first2
      [ [0..b) [ 0 2array ] map ]
      [ 1 (a..b] [ 0 swap 2array ] map ] bi* append ;
    
    : slash ( rows origin -- line )
      first2
      [ 0 [a..b] ]
      [ pick dimension last [a..b) ] bi* zip
      swap matrix-nths ;
    
    : backslash ( rows origin -- line )
      [ dup dimension ] dip first2
      [ over first [a..b) ]
      [ pick last [a..b) ] bi* zip nip
      swap matrix-nths ;
    
    : slashes ( rows -- lines )
      dup slash-origins
      [ slash ] with map ;
    
    : backslashes ( rows -- lines )
      dup backslash-origins
      [ backslash ] with map ;
    
    : word-count ( line word -- n )
      dupd [ reverse ] dip
      '[ _ subseq-indices length ] bi@ + ;
    
    : part1 ( -- n )
      get-input
      { [ ] [ verticals ] [ slashes ] [ backslashes ] } cleave-array concat
      [ "XMAS" word-count ] map-sum ;
    
    : origin-adistances ( rows origins line-quot: ( rows origin -- line ) -- origin-adistances-assoc )
      with zip-with
      "MAS" "SAM" [ '[ [ _ subseq-indices ] map-values ] ] bi@ bi append
      harvest-values
      [ [ 1 + ] map ] map-values ; inline
    
    : a-coords ( origin-adistances coord-quot: ( adistance -- row-delta col-delta ) -- coords )
      '[ first2 [ @ 2array v+ ] with map ] map-concat ; inline
    
    : slash-a-coords ( rows -- coords )
      dup slash-origins [ slash ] origin-adistances
      [ [ 0 swap - ] keep ] a-coords ;
    
    : backslash-a-coords ( rows -- coords )
      dup backslash-origins [ backslash ] origin-adistances
      [ dup ] a-coords ;
    
    : part2 ( -- n )
      get-input [ slash-a-coords ] [ backslash-a-coords ] bi
      intersect length ;
    

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