23th day

Author: majcn

day23/day23.go

@@ -0,0 +1,135 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	. "majcn.si/advent-of-code-2022/util"
+)
+
+type DataType Set[Location]
+
+func parseData(data string) DataType {
+	dataSplit := strings.Split(data, "\n")
+
+	result := make(Set[Location])
+	for y, line := range dataSplit {
+		for x, v := range line {
+			if v == '#' {
+				result.Add(Location{X: x, Y: y})
+			}
+		}
+	}
+
+	return DataType(result)
+}
+
+func getNextLocation(elfs Set[Location], elf Location, priorities []byte) Location {
+	hasNoNeighbours := true
+	for _, neighbour := range GetNeighbours8() {
+		newLocation := elf.Add(neighbour)
+		if elfs.Contains(newLocation) {
+			hasNoNeighbours = false
+			break
+		}
+	}
+
+	if hasNoNeighbours {
+		return elf
+	}
+
+	for _, priority := range priorities {
+		switch priority {
+		case 'N':
+			if !elfs.Contains(elf.Add(Location{X: -1, Y: -1})) && !elfs.Contains(elf.Add(Location{X: 0, Y: -1})) && !elfs.Contains(elf.Add(Location{X: 1, Y: -1})) {
+				return elf.Add(Location{X: 0, Y: -1})
+			}
+		case 'S':
+			if !elfs.Contains(elf.Add(Location{X: -1, Y: 1})) && !elfs.Contains(elf.Add(Location{X: 0, Y: 1})) && !elfs.Contains(elf.Add(Location{X: 1, Y: 1})) {
+				return elf.Add(Location{X: 0, Y: 1})
+			}
+		case 'W':
+			if !elfs.Contains(elf.Add(Location{X: -1, Y: -1})) && !elfs.Contains(elf.Add(Location{X: -1, Y: 0})) && !elfs.Contains(elf.Add(Location{X: -1, Y: 1})) {
+				return elf.Add(Location{X: -1, Y: 0})
+			}
+		case 'E':
+			if !elfs.Contains(elf.Add(Location{X: 1, Y: -1})) && !elfs.Contains(elf.Add(Location{X: 1, Y: 0})) && !elfs.Contains(elf.Add(Location{X: 1, Y: 1})) {
+				return elf.Add(Location{X: 1, Y: 0})
+			}
+		}
+	}
+
+	return elf
+}
+
+func solvePartX(data DataType, goal func(int, bool) bool) (int, Set[Location]) {
+	priorities := [][]byte{
+		{'N', 'S', 'W', 'E'},
+		{'S', 'W', 'E', 'N'},
+		{'W', 'E', 'N', 'S'},
+		{'E', 'N', 'S', 'W'},
+	}
+
+	elfs := make(Set[Location], len(data))
+	for el := range data {
+		elfs.Add(el)
+	}
+
+	for i := 0; ; i++ {
+		blockedLocationsSet := make(Set[Location])
+		nextLocations := make(map[Location]Location)
+		for elf := range elfs {
+			nextElfLocation := getNextLocation(elfs, elf, priorities[i%4])
+			if elf == nextElfLocation {
+				continue
+			}
+
+			if blockedLocationsSet.Contains(nextElfLocation) {
+				continue
+			}
+
+			if _, ok := nextLocations[nextElfLocation]; ok {
+				blockedLocationsSet.Add(nextElfLocation)
+				delete(nextLocations, nextElfLocation)
+				continue
+			}
+
+			nextLocations[nextElfLocation] = elf
+		}
+
+		for nextLocation, prevLocation := range nextLocations {
+			elfs.Remove(prevLocation)
+			elfs.Add(nextLocation)
+		}
+
+		if goal(i+1, len(nextLocations) == 0) {
+			return i + 1, elfs
+		}
+	}
+}
+
+func solvePart1(data DataType) (rc int) {
+	_, elfs := solvePartX(data, func(i int, _ bool) bool { return i == 10 })
+
+	minx, maxx, miny, maxy := MaxInt, 0, MaxInt, 0
+	for elf := range elfs {
+		minx = Min(minx, elf.X)
+		maxx = Max(maxx, elf.X)
+		miny = Min(miny, elf.Y)
+		maxy = Max(maxy, elf.Y)
+	}
+
+	return (maxy-miny+1)*(maxx-minx+1) - len(elfs)
+}
+
+func solvePart2(data DataType) (rc int) {
+	rc, _ = solvePartX(data, func(_ int, nothingHappens bool) bool { return nothingHappens })
+
+	return
+}
+
+func main() {
+	data := parseData(FetchInputData(23))
+	fmt.Println(solvePart1(data))
+	fmt.Println(solvePart2(data))
+}

day23/day23_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"os"
+	"testing"
+
+	. "majcn.si/advent-of-code-2022/util"
+)
+
+func ExpectedPart1() int {
+	return 110
+}
+
+func ExpectedPart2() int {
+	return 20
+}
+
+var data DataType
+
+func init() {
+	input, _ := os.ReadFile("../examples/23.txt")
+	data = parseData(string(input))
+}
+
+func TestPart1(t *testing.T) {
+	AssertTestPartX(t, ExpectedPart1(), solvePart1(data))
+}
+
+func TestPart2(t *testing.T) {
+	AssertTestPartX(t, ExpectedPart2(), solvePart2(data))
+}

examples/23.txt

@@ -0,0 +1,7 @@
+....#..
+..###.#
+#...#.#
+.#...##
+#.###..
+##.#.##
+.#..#..