day17 done

Author: analogrelay

2020/day17/day17.go

@@ -1,7 +1,218 @@
 package day17
 
-import "fmt"
+import (
+	"fmt"
+	"math"
+)
 
 func Run(lines []string) error {
-    return fmt.Errorf("not yet implemented")
+	dimension, err := ParseBoard(lines, false)
+	if err != nil {
+		return err
+	}
+
+	for i := 0; i < 6; i++ {
+		dimension = dimension.Step()
+	}
+
+	activeCells := dimension.GetActiveCells()
+	fmt.Println("Part 1:", len(activeCells))
+
+	dimension, err = ParseBoard(lines, true)
+	if err != nil {
+		return err
+	}
+
+	for i := 0; i < 6; i++ {
+		dimension = dimension.Step()
+	}
+
+	activeCells = dimension.GetActiveCells()
+	fmt.Println("Part 2:", len(activeCells))
+	return nil
+}
+
+type hyperCubeMap map[int]cubeMap
+type cubeMap map[int]planeMap
+type planeMap map[int]rowMap
+type rowMap map[int]bool
+type Point struct{ X, Y, Z, W int }
+
+type Range struct {
+	Min int
+	Max int
+}
+
+var EmptyRange = Range{math.MaxInt32, math.MinInt32}
+
+type PocketDimension struct {
+	cubes    hyperCubeMap
+	xRange   Range
+	yRange   Range
+	zRange   Range
+	wRange   Range
+	includeW bool
+}
+
+func NewPocketDimension(includeW bool) PocketDimension {
+	wRange := Range{0, 0}
+	if includeW {
+		wRange = Range{-1, 1}
+	}
+
+	return PocketDimension{
+		cubes:    make(hyperCubeMap),
+		xRange:   Range{-1, 1},
+		yRange:   Range{-1, 1},
+		zRange:   Range{-1, 1},
+		wRange:   wRange,
+		includeW: includeW,
+	}
+}
+
+func ParseBoard(lines []string, includeW bool) (PocketDimension, error) {
+	dimension := NewPocketDimension(includeW)
+	for y, line := range lines {
+		for x, cell := range line {
+			switch cell {
+			case '.':
+				dimension.SetCell(x, y, 0, 0, false)
+			case '#':
+				dimension.SetCell(x, y, 0, 0, true)
+			default:
+				return dimension, fmt.Errorf("invalid cell '%v'", cell)
+			}
+		}
+	}
+	return dimension, nil
+}
+
+func (p *PocketDimension) Step() PocketDimension {
+	newDimension := NewPocketDimension(p.includeW)
+	p.eachCell(func(x, y, z, w int) {
+		val := p.stepCell(x, y, z, w)
+		newDimension.SetCell(x, y, z, w, val)
+	})
+	// fmt.Println("===")
+	return newDimension
+}
+func (p *PocketDimension) GetActiveCells() []Point {
+	activeCells := []Point{}
+	p.eachCell(func(x, y, z, w int) {
+		if p.GetCell(x, y, z, w) {
+			activeCells = append(activeCells, Point{x, y, z, w})
+		}
+	})
+	return activeCells
+}
+
+func (p *PocketDimension) stepCell(x, y, z, w int) bool {
+	current := p.GetCell(x, y, z, w)
+	activeNeighbors := 0
+	for _, neighbor := range getNeighbors(p.includeW) {
+		if p.GetCell(x+neighbor.X, y+neighbor.Y, z+neighbor.Z, w+neighbor.W) {
+			activeNeighbors++
+		}
+	}
+
+	// fmt.Printf("(%d, %d, %d) has %d active neighbors => ", x, y, z, activeNeighbors)
+	if activeNeighbors == 3 || (current && activeNeighbors == 2) {
+		// fmt.Println("active")
+		return true
+	}
+	// fmt.Println("inactive")
+	return false
+}
+
+func (p *PocketDimension) eachCell(fn func(x, y, z, w int)) {
+	for z := p.zRange.Min; z <= p.zRange.Max; z++ {
+		for y := p.yRange.Min; y <= p.yRange.Max; y++ {
+			for x := p.xRange.Min; x <= p.xRange.Max; x++ {
+				for w := p.wRange.Min; w <= p.wRange.Max; w++ {
+					fn(x, y, z, w)
+				}
+			}
+		}
+	}
+}
+
+func (p *PocketDimension) SetCell(x, y, z, w int, value bool) {
+	if !p.includeW && w != 0 {
+		panic("tried to set non-zero w in 3d-cube!")
+	}
+
+	cube, ok := p.cubes[w]
+	if !ok {
+		cube = make(cubeMap)
+		p.cubes[w] = cube
+	}
+
+	plane, ok := cube[z]
+	if !ok {
+		plane = make(planeMap)
+		cube[z] = plane
+	}
+
+	row, ok := plane[y]
+	if !ok {
+		row = make(rowMap)
+		plane[y] = row
+	}
+
+	row[x] = value
+	p.zRange = updateRange(p.zRange, z, 1)
+	p.yRange = updateRange(p.yRange, y, 1)
+	p.xRange = updateRange(p.xRange, x, 1)
+
+	if p.includeW {
+		p.wRange = updateRange(p.wRange, w, 1)
+	}
+}
+
+func updateRange(rg Range, val int, delta int) Range {
+	if val <= rg.Min {
+		return Range{Min: val - delta, Max: rg.Max}
+	} else if val >= rg.Max {
+		return Range{Min: rg.Min, Max: val + delta}
+	} else {
+		return rg
+	}
+}
+
+func (p *PocketDimension) GetCell(x, y, z, w int) bool {
+	if !p.includeW && w != 0 {
+		panic("tried to access non-zero w in 3d cube!")
+	}
+
+	if cube, ok := p.cubes[w]; ok {
+		if plane, ok := cube[z]; ok {
+			if row, ok := plane[y]; ok {
+				if cell, ok := row[x]; ok {
+					return cell
+				}
+			}
+		}
+	}
+	return false
+}
+
+func getNeighbors(includeW bool) []Point {
+	startW, maxW := 0, 0
+	if includeW {
+		startW, maxW = -1, 1
+	}
+
+	result := []Point{}
+	for x := -1; x <= 1; x++ {
+		for y := -1; y <= 1; y++ {
+			for z := -1; z <= 1; z++ {
+				for w := startW; w <= maxW; w++ {
+					if x != 0 || y != 0 || z != 0 || w != 0 {
+						result = append(result, Point{x, y, z, w})
+					}
+				}
+			}
+		}
+	}
+	return result
 }

2020/day17/day17_test.go

@@ -1 +1,59 @@
 package day17
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestNeighbors(t *testing.T) {
+	doTestNeighbors(t, 26, false)
+	doTestNeighbors(t, 80, true)
+}
+
+func doTestNeighbors(t *testing.T, count int, includeW bool) {
+	neighbors := getNeighbors(includeW)
+	require.Equal(t, count, len(neighbors))
+	for _, cell := range neighbors {
+		matches := 0
+		for _, other := range neighbors {
+			if cell.X == other.X && cell.Y == other.Y && cell.Z == other.Z && cell.W == other.W {
+				matches++
+			}
+		}
+		require.Equal(t, 1, matches)
+	}
+}
+
+func TestStep(t *testing.T) {
+	dimension, err := ParseBoard([]string{
+		".#.",
+		"..#",
+		"###",
+	}, false)
+	require.NoError(t, err)
+	require.ElementsMatch(t, []Point{
+		{1, 0, 0, 0},
+		{2, 1, 0, 0},
+		{0, 2, 0, 0},
+		{1, 2, 0, 0},
+		{2, 2, 0, 0},
+	}, dimension.GetActiveCells())
+
+	dimension = dimension.Step()
+	activeCells := dimension.GetActiveCells()
+	require.Equal(t, 11, len(activeCells))
+
+	dimension = dimension.Step()
+	activeCells = dimension.GetActiveCells()
+	require.Equal(t, 21, len(activeCells))
+
+	dimension = dimension.Step()
+	activeCells = dimension.GetActiveCells()
+	require.Equal(t, 38, len(activeCells))
+
+	for i := 0; i < 3; i++ {
+		dimension = dimension.Step()
+	}
+	require.Equal(t, 112, len(dimension.GetActiveCells()))
+}

2020/day17/input.txt

@@ -0,0 +1,8 @@
+...###.#
+#.#.##..
+.##.##..
+..##...#
+.###.##.
+.#..##..
+.....###
+.####..#