78 lines
2.1 KiB
Nim
78 lines
2.1 KiB
Nim
import ./common, std/[sequtils, algorithm, sugar, sets, strformat, strutils, tables]
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type
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Lines = seq[string]
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Path = seq[string]
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NodeSet = HashSet[string]
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Graph = Table[string, NodeSet]
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proc toGraph(lines: Lines): Graph =
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for l in lines:
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let nodes = l.split "-"
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if result.hasKey nodes[0]: result[nodes[0]].incl nodes[1]
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else: result[nodes[0]] = toHashSet [nodes[1]]
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if result.hasKey nodes[1]: result[nodes[1]].incl nodes[0]
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else: result[nodes[1]] = toHashSet [nodes[0]]
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proc basicIneligibleNodes(path: Path): NodeSet =
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for n in path:
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if n in ["start", "end"] or n.toUpper != n:
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result.incl n
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proc part2IneligibleNodes(path: Path): NodeSet =
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# determine if we've double visited any small caves yet
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var hasVisitedSingleSmallCaveTwice: bool = path.filterIt(not (it in ["start", "end"]) and it != it.toUpper).toCountTable.values.toSeq.anyIt(it >= 2)
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for n in path:
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let isStartOrEnd = n == "start" or n == "end"
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let isSmall = n.toUpper != n
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if isStartOrEnd or (isSmall and hasVisitedSingleSmallCaveTwice): result.incl n
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# TODO: tail-call optimization?
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proc visit(node: string, graph: Graph, ineligibleNodesReducer: (Path) -> NodeSet, path: Path = @[]): int =
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if node == "end": return 1
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let newPath = path & @[node]
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let forbiddenNodes = newPath.ineligibleNodesReducer()
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let toVisit = graph[node] - forbiddenNodes
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for n in toVisit: result += visit(n, graph, ineligibleNodesReducer, newPath)
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proc pathing(input: seq[string]): int =
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visit("start", input.toGraph, basicIneligibleNodes)
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proc pathing2(input: seq[string]): int =
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visit("start", input.toGraph, part2IneligibleNodes)
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const smallTestInput = @[
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"start-A",
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"start-b",
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"A-c",
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"A-b",
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"b-d",
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"A-end",
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"b-end",
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]
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const stest = (smallTestInput, 10, 36)
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# const largeTestInput = @[
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# "fs-end",
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# "he-DX",
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# "fs-he",
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# "start-DX",
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# "pj-DX",
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# "end-zg",
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# "zg-sl",
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# "zg-pj",
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# "pj-he",
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# "RW-he",
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# "fs-DX",
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# "pj-RW",
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# "zg-RW",
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# "start-pj",
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# "he-WI",
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# "zg-he",
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# "pj-fs",
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# "start-RW",
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# ]
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#
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# const ltest = (largeTestInput, 225, 3509)
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doDay 12, n => n.loadInput, pathing, pathing2, stest
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