this post was submitted on 04 Dec 2024
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Advent Of Code

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๐ŸŒš - 2024 DAY 4 SOLUTIONS - ๐ŸŒš (programming.dev)
submitted 3 weeks ago by [email protected] to c/[email protected]
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Day 4: Ceres Search

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[โ€“] [email protected] 1 points 2 weeks ago

Smalltalk

I could have done it in 2 fns if I made them more generic, but couldn't be bothered

day4p1: input
    | lines sum w h|
    
    sum := ('XMAS' asRegex matchesIn: input) size. "forward"
    sum := sum + ('SAMX' asRegex matchesIn: input) size. "backwards sep cause overlapping"
    
    lines := input lines.
    h := lines size.
    w := (lines at: 1) size.
    
    1 to: h-3 do: [ :p1 |
        1 to: w do: [ :p2 |
            sum := sum + (self d4diag: lines p1: p1 p2: p2 dir: -1).
            sum := sum + (self d4diag: lines p1: p1 p2: p2 dir: 0).
            sum := sum + (self d4diag: lines p1: p1 p2: p2 dir: 1).    
        ]
    ].
    
    ^ sum.

d4diag: input p1: p1 p2: p2 dir: dir
    | reverse xm ii |
    
    xm := 'XMAS'.
    
    reverse := ((input at: p1) at: p2) = $S.
    
    0 to: 3 do: [ :i |
        ii := reverse ifTrue: [ 4 - i ] ifFalse: [ i + 1 ].
                                                    "if out of bounds, obv not possible"
        ((xm at: ii) = ((input at: p1 + i) at: i * dir + p2 ifAbsent: [^ 0])) ifFalse: [^ 0]
    ].

    ^ 1.

Part 2

day4p2: input
    | lines sum w h pos |
    "Find all diag mas, then check of 1 . -1 (we can look back on every -1"
    
    sum := 0.
    lines := input lines.
    h := lines size.
    w := (lines at: 1) size.
    
    1 to: h-2 do: [ :p1 |
        pos := Array new: w withAll: false.
        1 to: w do: [ :p2 |
            (self d42: lines p1: p1 p2: p2 dir: -1)
                ifTrue: [
                    sum := sum + ((pos at: p2-2) ifTrue:[1] ifFalse:[0]).
                ].
            
            (self d42: lines p1: p1 p2: p2 dir: 1) ifTrue: [pos at: p2 put: true].
        ]
    ].
    
    ^ sum.

d42: input p1: p1 p2: p2 dir: dir
    | reverse xm ii |
    
    xm := 'MAS'.
    
    reverse := ((input at: p1) at: p2) = $S.
    
    0 to: 2 do: [ :i |
        ii := reverse ifTrue: [ 3 - i ] ifFalse: [ i + 1 ].
                                                    "if out of bounds, obv not possible"
        ((xm at: ii) = ((input at: p1 + i) at: i * dir + p2 ifAbsent: [^ false])) ifFalse: [^ false]
    ].

    ^ true.