feat: Solving day 6

Author: truggeri

src/day6/day6.go

@@ -1,5 +1,125 @@
 package day6
 
+import (
+	"slices"
+	"strings"
+)
+
+type direction uint
+
+const (
+	Up direction = iota
+	Right
+	Down
+	Left
+)
+
+type room struct {
+	layout [][]square
+	guard  guard
+}
+
+type square struct {
+	visited  bool
+	obstacle bool
+}
+
+type guard struct {
+	direction direction
+	location
+}
+
+type location struct {
+	x int
+	y int
+}
+
 func Solve(input string) uint {
-	return 41
+	rm := parseInput(input)
+	return solve(rm)
+}
+
+func parseInput(input string) room {
+	var rm room
+	for j, l := range strings.Split(input, "\n") {
+		rm.layout = slices.Insert(rm.layout, j, make([]square, 0))
+		for i, ch := range l {
+			sq := square{}
+			if ch == '#' {
+				sq.obstacle = true
+			} else if ch != '.' {
+				rm.guard = guard{
+					direction: parseDirection(ch),
+					location: location{
+						x: i,
+						y: j,
+					},
+				}
+				sq.visited = true
+			}
+			rm.layout[j] = slices.Insert(rm.layout[j], i, sq)
+		}
+	}
+	return rm
+}
+
+func parseDirection(input rune) direction {
+	switch input {
+	case '>':
+		return Right
+	case '<':
+		return Left
+	case 'v':
+		return Down
+	}
+	return Up
+}
+
+func solve(rm room) uint {
+	var moves, unique uint = 0, 1
+	nextLocation := rm.guard.location
+	for {
+		moves++
+		x, y := adjustLocation(rm.guard.direction)
+		nextLocation.x += x
+		nextLocation.y += y
+
+		if offGrid(nextLocation, rm) {
+			break
+		}
+
+		nextSquare := rm.layout[nextLocation.y][nextLocation.x]
+		if nextSquare.obstacle {
+			rm.guard.direction += 1
+			if rm.guard.direction > Left {
+				rm.guard.direction = Up
+			}
+			nextLocation = rm.guard.location
+		} else {
+			if !nextSquare.visited {
+				unique++
+				rm.layout[nextLocation.y][nextLocation.x].visited = true
+			}
+			rm.guard.location = nextLocation
+		}
+	}
+	return unique
+}
+
+func adjustLocation(input direction) (int, int) {
+	switch input {
+	case Right:
+		return 1, 0
+	case Left:
+		return -1, 0
+	case Down:
+		return 0, 1
+	case Up:
+		return 0, -1
+	}
+	return 0, 0
+}
+
+func offGrid(loc location, rm room) bool {
+	return loc.x < 0 || loc.y < 0 || loc.x >= len(rm.layout) || loc.y >= len(rm.layout[0])
 }