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Really slow day 12 part 2 solution

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Daniel Flanagan 2021-12-14 13:53:51 -06:00
parent a9e5391187
commit 8b63de7df5
Signed by: lytedev
GPG key ID: 5B2020A0F9921EF4
1 changed files with 35 additions and 19 deletions
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2021/nim/day12.nim
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@ -1,29 +1,45 @@
import ./common, std/[sequtils, algorithm, sugar, sets, strformat, strutils, tables]
proc toGraph(lines: seq[string]): Table[string, HashSet[string]] =
result = initTable[string, HashSet[string]]()
for l in lines:
let nodes = l.split("-")
if result.hasKey(nodes[0]): result[nodes[0]].incl(nodes[1])
else: result[nodes[0]] = toHashSet([nodes[1]])
if result.hasKey(nodes[1]): result[nodes[1]].incl(nodes[0])
else: result[nodes[1]] = toHashSet([nodes[0]])
type
Lines = seq[string]
Path = seq[string]
NodeSet = HashSet[string]
Graph = Table[string, NodeSet]
proc visit(curNode: string, graph: Table[string, HashSet[string]], visitedNodes: HashSet[string], hasVisitedSmallCaveTwice = true): int =
if curNode == "end": return 1
echo visitedNodes, curNode, " (", hasVisitedSmallCaveTwice, ")"
var isBig = curNode == curNode.toUpper()
if not isBig and not hasVisitedSmallCaveTwice and curNode != "start":
for node in (graph[curNode] - visitedNodes): result += visit(node, graph, visitedNodes, true)
var newVisitedNodes = visitedNodes
if not isBig: newVisitedNodes.incl(curNode)
for node in (graph[curNode] - visitedNodes): result += visit(node, graph, newVisitedNodes, hasVisitedSmallCaveTwice)
proc toGraph(lines: Lines): Graph =
for l in lines:
let nodes = l.split "-"
if result.hasKey nodes[0]: result[nodes[0]].incl nodes[1]
else: result[nodes[0]] = toHashSet [nodes[1]]
if result.hasKey nodes[1]: result[nodes[1]].incl nodes[0]
else: result[nodes[1]] = toHashSet [nodes[0]]
proc basicIneligibleNodes(path: Path): NodeSet =
for n in path:
if n in ["start", "end"] or n.toUpper != n:
result.incl n
proc part2IneligibleNodes(path: Path): NodeSet =
# determine if we've double visited any small caves yet
var hasVisitedSingleSmallCaveTwice: bool = path.filterIt(not (it in ["start", "end"]) and it != it.toUpper).toCountTable.values.toSeq.anyIt(it >= 2)
for n in path:
let isStartOrEnd = n == "start" or n == "end"
let isSmall = n.toUpper != n
if isStartOrEnd or (isSmall and hasVisitedSingleSmallCaveTwice): result.incl n
# TODO: tail-call optimization?
proc visit(node: string, graph: Graph, ineligibleNodesReducer: (Path) -> NodeSet, path: Path = @[]): int =
if node == "end": return 1
let newPath = path & @[node]
let forbiddenNodes = newPath.ineligibleNodesReducer()
let toVisit = graph[node] - forbiddenNodes
for n in toVisit: result += visit(n, graph, ineligibleNodesReducer, newPath)
proc pathing(input: seq[string]): int =
visit("start", input.toGraph, toHashSet[string]([]))
visit("start", input.toGraph, basicIneligibleNodes)
proc pathing2(input: seq[string]): int =
visit("start", input.toGraph, toHashSet[string]([]), false)
visit("start", input.toGraph, part2IneligibleNodes)
const smallTestInput = @[
"start-A",