aoc24/day16/dijkstra.go

package main

import (
	"fmt"
	"slices"

	"git.mstar.dev/mstar/aoc24/util"
	"git.mstar.dev/mstar/goutils/sliceutils"
)

type Crossing struct {
	At    util.Vec2
	Exits []util.Vec2
}

type Connection struct {
	From, To util.Vec2
	Distance int
}

var (
	DirUp    = util.Vec2{X: 0, Y: -1}
	DirRight = util.Vec2{X: 1, Y: 0}
	DirDown  = util.Vec2{X: 0, Y: 1}
	DirLeft  = util.Vec2{X: -1, Y: 0}
)

// Get the size of the bord
func getSize(lines []string) util.Vec2 {
	return util.Vec2{X: int64(len(lines[0])), Y: int64(len(lines))}
}

// Count the paths next to a given positon
func countPathsAt(lines [][]rune, at util.Vec2) []util.Vec2 {
	center := lines[at.Y][at.X]
	paths := []util.Vec2{}
	if center == '#' {
		return paths
	}
	if util.SafeGet(lines, at.Up()) != '#' {
		paths = append(paths, at.Up())
	}
	if util.SafeGet(lines, at.Down()) != '#' {
		paths = append(paths, at.Down())
	}
	if util.SafeGet(lines, at.Left()) != '#' {
		paths = append(paths, at.Left())
	}
	if util.SafeGet(lines, at.Right()) != '#' {
		paths = append(paths, at.Right())
	}
	return paths
}

func sortPaths(area [][]rune) (all, straights, bends, crossings, deadEnds []util.Vec2) {
	for iy, line := range area {
		for ix, char := range line {
			if char == '#' {
				continue
			}
			pos := util.Vec2{X: int64(ix), Y: int64(iy)}
			all = append(all, pos)
			entries := countPathsAt(area, pos)
			switch len(entries) {
			case 0:
				continue
			case 1:
				deadEnds = append(deadEnds, pos)
			case 2:
				if entries[0].Right().Right().Eq(entries[1]) ||
					entries[0].Left().Left().Eq(entries[1]) ||
					entries[0].Up().Up().Eq(entries[1]) ||
					entries[0].Down().Down().Eq(entries[1]) {
					straights = append(straights, pos)
				} else {
					bends = append(bends, pos)
				}
			case 3, 4:
				crossings = append(crossings, pos)
			default:
				continue
			}
		}
	}
	return
}

// Only works when at a not-straight path node (crossing, bend, dead end)
// TODO: Debug this
func findAdjacentTargets(at util.Vec2, crossings, bends, deadEnds []util.Vec2) []util.Vec2 {
	if sliceutils.Contains(crossings, at) || sliceutils.Contains(bends, at) ||
		sliceutils.Contains(deadEnds, at) {
		return []util.Vec2{}
	}
	crossingsPosX := sliceutils.Filter(
		crossings,
		func(t util.Vec2) bool { return at.X < t.X && at.Y == t.Y },
	)
	slices.SortFunc(crossingsPosX, func(a, b util.Vec2) int { return int(a.X - b.X) })
	crossingsNegX := sliceutils.Filter(
		crossings,
		func(t util.Vec2) bool { return at.X > t.X && at.Y == t.Y },
	)
	slices.SortFunc(crossingsNegX, func(a, b util.Vec2) int { return int(b.X - a.X) })
	crossingsPosY := sliceutils.Filter(
		crossings,
		func(t util.Vec2) bool { return at.Y < t.Y && at.X == t.X },
	)
	slices.SortFunc(crossingsPosY, func(a, b util.Vec2) int { return int(a.Y - b.Y) })
	crossingsNegY := sliceutils.Filter(
		crossings,
		func(t util.Vec2) bool { return at.Y > t.Y && at.X == t.X },
	)
	slices.SortFunc(crossingsNegY, func(a, b util.Vec2) int { return int(b.Y - a.Y) })
	bendsPosX := sliceutils.Filter(
		bends,
		func(t util.Vec2) bool { return at.X < t.X && at.Y == t.Y },
	)
	slices.SortFunc(bendsPosX, func(a, b util.Vec2) int { return int(a.X - b.X) })
	bendsNegX := sliceutils.Filter(
		bends,
		func(t util.Vec2) bool { return at.X > t.X && at.Y == t.Y },
	)
	slices.SortFunc(bendsNegX, func(a, b util.Vec2) int { return int(b.X - a.X) })
	bendsPosY := sliceutils.Filter(
		bends,
		func(t util.Vec2) bool { return at.Y < t.Y && at.X == t.X },
	)
	slices.SortFunc(bendsPosY, func(a, b util.Vec2) int { return int(a.Y - b.Y) })
	bendsNegY := sliceutils.Filter(
		bends,
		func(t util.Vec2) bool { return at.Y > t.Y && at.X == t.X },
	)
	slices.SortFunc(bendsNegY, func(a, b util.Vec2) int { return int(b.Y - a.Y) })
	deadEndsPosX := sliceutils.Filter(
		deadEnds,
		func(t util.Vec2) bool { return at.X < t.X && at.Y == t.Y },
	)
	slices.SortFunc(deadEndsPosX, func(a, b util.Vec2) int { return int(a.X - b.X) })
	deadEndsNegX := sliceutils.Filter(
		deadEnds,
		func(t util.Vec2) bool { return at.X > t.X && at.Y == t.Y },
	)
	slices.SortFunc(deadEndsNegX, func(a, b util.Vec2) int { return int(b.X - a.X) })
	deadEndsPosY := sliceutils.Filter(
		deadEnds,
		func(t util.Vec2) bool { return at.Y < t.Y && at.X == t.X },
	)
	slices.SortFunc(deadEndsPosY, func(a, b util.Vec2) int { return int(a.Y - b.Y) })
	deadEndsNegY := sliceutils.Filter(
		deadEnds,
		func(t util.Vec2) bool { return at.Y > t.Y && at.X == t.X },
	)
	slices.SortFunc(deadEndsNegY, func(a, b util.Vec2) int { return int(b.Y - a.Y) })

	combined := []util.Vec2{}
	combined = append(combined, crossingsPosX...)
	combined = append(combined, crossingsNegX...)
	combined = append(combined, crossingsPosY...)
	combined = append(combined, crossingsNegY...)
	combined = append(combined, bendsPosX...)
	combined = append(combined, bendsNegX...)
	combined = append(combined, bendsPosY...)
	combined = append(combined, bendsNegY...)
	combined = append(combined, deadEndsPosX...)
	combined = append(combined, deadEndsNegX...)
	combined = append(combined, deadEndsPosY...)
	combined = append(combined, deadEndsNegY...)
	return combined
}

func distanceBetween(start, end util.Vec2, crossings, bends, deadEnds []util.Vec2) (int, bool) {
	score := -1
	if start.Eq(end) {
		return 0, true
	}
	crossings = sliceutils.Filter(crossings, func(v util.Vec2) bool { return !v.Eq(start) })
	return score, false
}

func followBend(
	at, from util.Vec2,
	crossings, bends, deadEnds []util.Vec2,
) (nextCrossingOrDeadEnd util.Vec2, distanceTravelled int) {
	if sliceutils.Contains(crossings, at) {
		return at, 0
	}
	return at, 0
}

func main() {
	inputLines := util.FileContentToNonEmptyLines(util.LoadFileFromArgs())
	// size := getSize(inputLines)
	area := sliceutils.Map(inputLines, func(t string) []rune { return []rune(t) })
	_, _, bends, crossings, deadEnds := sortPaths(area)
	// fmt.Println("straights:", straights)
	fmt.Println("bends:", bends)
	fmt.Println("crossings:", crossings)
	fmt.Println("dead ends:", deadEnds)
	fmt.Println("adjacent:", findAdjacentTargets(crossings[0], crossings, bends, deadEnds))
}