75 lines
2.4 KiB
Smalltalk
75 lines
2.4 KiB
Smalltalk
Object subclass: MemorySpace [
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| corruption origin dirs end
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grid size queue |
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initialize
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[ origin := Posn x: 1 y: 1.
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dirs := {Posn up. Posn down. Posn left. Posn right} ]
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corruption: n [corruption := n collect: [:it | it + origin]]
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corruption [^corruption]
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findExitWithInitial: initial
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[ | steps stepsInitial |
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size := 71.
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grid := Grid width: size height: size initWith: [
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:i | {"blocked at: "FloatD infinity.
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"last reachable before: "nil}].
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corruption keysAndValuesDo: [
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:time :pos | (grid at: pos) at: 1 put: time ].
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queue := LookupTable new.
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self enqueue: origin withLastTime: ((grid at: origin) at: 1).
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steps := 0.
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end := Posn x: size y: size.
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[ queue isEmpty ] whileFalse: [
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self stepOnce.
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steps := steps + 1.
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(stepsInitial isNil and: [
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((grid at: end) at: 2)
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ifNil: [false]
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ifNotNil: [:it | it > initial]]) ifTrue: [
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stepsInitial := steps.
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].
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].
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^stepsInitial ]
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posnThatBlocksEnd [ ^(corruption at: ((grid at: end) at: 2)) - origin ]
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stepOnce
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[ | oldQueue |
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oldQueue := queue.
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queue := LookupTable new.
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oldQueue keysAndValuesDo: [
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:posn :time | dirs do: [
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:dir | self enqueue: posn + dir withLastTime: time ]]]
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enqueue: posn withLastTime: lastTime
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[ | entry bestTime |
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entry := grid at: posn.
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entry ifNil: [^false].
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bestTime := lastTime min: (entry at: 1).
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(entry at: 2) ifNotNil: [
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:prevLastReachable |
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bestTime > prevLastReachable ifFalse: [^false]].
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entry at: 2 put: bestTime.
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queue at: posn put: bestTime.
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^true ]
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plotAtTime: time
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[ | g | g := Grid width: size height: size initWith: [:i | $.].
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g rows: (g rows collect: [:it | it asString]).
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1 to: time do: [:i | g at: (corruption at: i) put: $#].
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g printNl ]
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]
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AOC input: [ | posns |
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posns := stdin toLines asArray collect: [
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:it | it scanf: '%d,%d' with: [:x :y | Posn x: x y: y]].
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MemorySpace new corruption: posns ];
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part1: [ :space | space findExitWithInitial: 1024 ];
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part2: [ :space | | p | p := space posnThatBlocksEnd.
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'%1,%2' % {p x . p y} ];
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result: [ :space :part | part value: space ];
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finish
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