Implementations for day 10

aoc2018.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"github.com/nlowe/aoc2018/day10"
 	"github.com/nlowe/aoc2018/day9"
 	"os"
 	"time"
@@ -57,6 +58,7 @@ func main() {
 		day7.A, day7.B,
 		day8.A, day8.B,
 		day9.A, day9.B,
+		day10.A,
 	)
 
 	flags := rootCmd.PersistentFlags()

day10/day10.go

@@ -0,0 +1,158 @@
+package day10
+
+import (
+	"fmt"
+	"github.com/nlowe/aoc2018/util"
+	"github.com/spf13/cobra"
+	"strconv"
+	"strings"
+)
+
+// We calculate the solution for 10b during 10a anyways. Since most of the code is re-used,
+// they're just setup as aliases of eachOther
+var A = &cobra.Command{
+	Use:   "10a",
+	Aliases: []string{"10b"},
+	Short: "Day 10, Problem A",
+	Run: func(_ *cobra.Command, _ []string) {
+		fmt.Printf("Answer: \n\n%s\n", a(util.ReadInput(), SolutionLetterHeight))
+	},
+}
+
+const TestLetterHeight = 8
+const SolutionLetterHeight = 10
+
+type point struct {
+	x int
+	y int
+	vx int
+	vy int
+}
+
+type bitmap struct {
+	pixels map[int]map[int] bool
+	minX int
+	minY int
+	maxX int
+	maxY int
+}
+
+func parsePoint(line string) *point {
+	components := strings.Split(line, "> velocity=<")
+	p := strings.Split(strings.TrimRight(components[0][10:], ">"), ",")
+	v := strings.Split(strings.TrimRight(components[1], ">"), ",")
+
+	result := &point{}
+
+	if x, err := strconv.Atoi(strings.TrimSpace(p[0])); err != nil {
+		panic(err)
+	} else {
+		result.x = x
+	}
+
+	if y, err := strconv.Atoi(strings.TrimSpace(p[1])); err != nil {
+		panic(err)
+	} else {
+		result.y = y
+	}
+
+	if vx, err := strconv.Atoi(strings.TrimSpace(v[0])); err != nil {
+		panic(err)
+	} else {
+		result.vx = vx
+	}
+
+	if vy, err := strconv.Atoi(strings.TrimSpace(v[1])); err != nil {
+		panic(err)
+	} else {
+		result.vy = vy
+	}
+
+	return result
+}
+
+// This is the best test I could come up with that works for tests and real inputs
+// TODO: Figure out a better test
+func isProbableSolution(height int, points []*point) bool {
+	bitmap := mapIt(points)
+
+	return bitmap.maxY - bitmap.minY == height - 1
+}
+
+func mapIt(points []*point) *bitmap {
+	minX := points[0].x
+	minY := points[0].y
+	maxX := points[0].x
+	maxY := points[0].y
+
+	pixels := map[int]map[int]bool{}
+
+	for _, p := range points {
+		if _, found := pixels[p.x]; !found {
+			pixels[p.x] = map[int]bool{}
+		}
+
+		pixels[p.x][p.y] = true
+
+		if p.x < minX {
+			minX = p.x
+		}
+
+		if p.x > maxX {
+			maxX = p.x
+		}
+
+		if p.y < minY {
+			minY = p.y
+		}
+
+		if p.y > maxY {
+			maxY = p.y
+		}
+	}
+
+	return &bitmap{pixels:pixels, minX: minX, minY: minY, maxX: maxX, maxY: maxY}
+}
+
+func prettyPrint(points []*point) string {
+	bitmap := mapIt(points)
+
+
+	builder := strings.Builder{}
+	for y := bitmap.minY; y <= bitmap.maxY; y++ {
+		line := strings.Builder{}
+
+		for x := bitmap.minX; x <= bitmap.maxX; x++ {
+			if _, found := bitmap.pixels[x]; found && bitmap.pixels[x][y] {
+				line.WriteRune('#')
+			} else {
+				line.WriteRune('.')
+			}
+		}
+
+		builder.WriteString(line.String())
+		builder.WriteRune('\n')
+	}
+
+	return strings.TrimSpace(builder.String())
+}
+
+func a(input *util.ChallengeInput, targetHeight int) string {
+	var points []*point
+	for line := range input.Lines() {
+		points = append(points, parsePoint(line))
+	}
+
+	steps := 0
+	for !isProbableSolution(targetHeight, points) {
+		steps += 1
+		for _, p := range points {
+			p.x += p.vx
+			p.y += p.vy
+		}
+	}
+
+	fmt.Printf("Solution found after %d steps\n", steps)
+
+	return prettyPrint(points)
+}

day10/day10_test.go

@@ -0,0 +1,52 @@
+package day10
+
+import (
+	"github.com/nlowe/aoc2018/util"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func TestA(t *testing.T) {
+	input := util.TestInput(`position=< 9,  1> velocity=< 0,  2>
+position=< 7,  0> velocity=<-1,  0>
+position=< 3, -2> velocity=<-1,  1>
+position=< 6, 10> velocity=<-2, -1>
+position=< 2, -4> velocity=< 2,  2>
+position=<-6, 10> velocity=< 2, -2>
+position=< 1,  8> velocity=< 1, -1>
+position=< 1,  7> velocity=< 1,  0>
+position=<-3, 11> velocity=< 1, -2>
+position=< 7,  6> velocity=<-1, -1>
+position=<-2,  3> velocity=< 1,  0>
+position=<-4,  3> velocity=< 2,  0>
+position=<10, -3> velocity=<-1,  1>
+position=< 5, 11> velocity=< 1, -2>
+position=< 4,  7> velocity=< 0, -1>
+position=< 8, -2> velocity=< 0,  1>
+position=<15,  0> velocity=<-2,  0>
+position=< 1,  6> velocity=< 1,  0>
+position=< 8,  9> velocity=< 0, -1>
+position=< 3,  3> velocity=<-1,  1>
+position=< 0,  5> velocity=< 0, -1>
+position=<-2,  2> velocity=< 2,  0>
+position=< 5, -2> velocity=< 1,  2>
+position=< 1,  4> velocity=< 2,  1>
+position=<-2,  7> velocity=< 2, -2>
+position=< 3,  6> velocity=<-1, -1>
+position=< 5,  0> velocity=< 1,  0>
+position=<-6,  0> velocity=< 2,  0>
+position=< 5,  9> velocity=< 1, -2>
+position=<14,  7> velocity=<-2,  0>
+position=<-3,  6> velocity=< 2, -1>`)
+
+	expected := `#...#..###
+#...#...#.
+#...#...#.
+#####...#.
+#...#...#.
+#...#...#.
+#...#...#.
+#...#..###`
+
+	require.Equal(t, expected, a(input, TestLetterHeight))
+}