59 lines
1.3 KiB
Nim
59 lines
1.3 KiB
Nim
import std/[sequtils, strscans, strutils, sugar, tables]
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type
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Map = tuple
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instructions: string
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nodes: Table[string, tuple[l: string, r: string]]
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func walk(map: Map, startingNodes: seq[string]): int =
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let il = map.instructions.len
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var
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p = 0
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nodes = startingNodes
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while true:
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let i = map.instructions[p mod il]
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nodes = block:
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var newNodes: seq[string]
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if i == 'L':
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for node in nodes:
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newNodes.add(map.nodes[node].l)
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else:
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for node in nodes:
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newNodes.add(map.nodes[node].r)
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newNodes
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p += 1
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if nodes.allIt(it[^1] == 'Z'):
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return p
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if p mod 1_000_000 == 0:
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debugEcho p
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func parse(input: string): Map =
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let
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sp = input.split("\n\n")
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nodeLines = sp[1].splitLines
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result.instructions = sp[0]
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var n, l, r: string
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for line in nodeLines:
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discard scanf(line, "$* = ($*, $*)", n, l, r)
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result.nodes[n] = (l, r)
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proc p1(input: string) =
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let startingNodes = @["AAA"]
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echo input.parse().walk(startingNodes)
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proc p2(input: string) =
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let
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map = input.parse()
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let
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startingNodes = collect:
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for k in map.nodes.keys:
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if k[^1] == 'A':
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k
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echo startingNodes
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echo map.walk(startingNodes)
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when isMainModule:
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let input = stdin.readAll().strip()
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p1(input)
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#p2(input) # takes too much time
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