Commit 740bc00

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Optimize 2024 day 20 part 2 by not creating set

All cheats are unique by construction.

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-6

lines changed

src
- main/scala/eu/sim642/adventofcode2024
  - Day20.scala
- test/scala/eu/sim642/adventofcode2024
  - Day20Test.scala

-6

lines changed

Lines changed: 3 additions & 5 deletions

Original file line number	Diff line number	Diff line change
`@@ -28,17 +28,15 @@ object Day20 {`
`28`	`28`	`trait Part {`
`29`	`29`	`val maxCheat: Int`
`30`	`30`
`31`		`- def findCheats(grid: Grid[Char]): Set[Cheat] = {`
	`31`	`+ def findCheats(grid: Grid[Char]): Iterable[Cheat] = {`
`32`	`32`	`val forwardSearch = gridGraphSearch(grid, 'S', 'E')`
`33`	`33`	`val forwardResult = BFS.search(forwardSearch)`
`34`	`34`	`val backwardSearch = gridGraphSearch(grid, 'E', 'S')`
`35`	`35`	`val backwardResult = BFS.search(backwardSearch)`
`36`	`36`
`37`	`37`	`val noCheatDistance = forwardResult.target.get._2`
`38`	`38`
`39`		`- // TODO: optimize`
`40`		`-`
`41`		`- (for {`
	`39`	`+ for {`
`42`	`40`	`(row, y) <- grid.view.zipWithIndex`
`43`	`41`	`(cell, x) <- row.view.zipWithIndex`
`44`	`42`	`if cell != '#'`
`@@ -55,7 +53,7 @@ object Day20 {`
`55`	`53`	`cheatDistance = forwardResult.distances(start) + (startCheat + endCheat) + backwardResult.distances(end)`
`56`	`54`	`//if cheatDistance <= noCheatDistance`
`57`	`55`	`save = noCheatDistance - cheatDistance`
`58`		`- } yield Cheat(start, end, save)).toSet`
	`56`	`+ } yield Cheat(start, end, save)`
`59`	`57`	`}`
`60`	`58`
`61`	`59`	`def countGoodCheats(grid: Grid[Char]): Int = findCheats(grid).count(_.save >= 100)`

Lines changed: 1 addition & 1 deletion

Original file line number	Diff line number	Diff line change
`@@ -60,7 +60,7 @@ class Day20Test extends AnyFunSuite {`
`60`	`60`	`assert(cheats(76) == 3)`
`61`	`61`	`}`
`62`	`62`
`63`		`- test("Part 2 input answer") {// TODO: optimize (~4.3s)`
	`63`	`+ test("Part 2 input answer") {`
`64`	`64`	`assert(Part2.countGoodCheats(parseGrid(input)) == 1011325)`
`65`	`65`	`}`
`66`	`66`	`}`

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