Implementation for 10a

challenge/day10/a.go

@@ -0,0 +1,97 @@
+package day10
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/nlowe/aoc2019/challenge"
+	"github.com/spf13/cobra"
+)
+
+const symAsteroid = '#'
+
+var A = &cobra.Command{
+	Use:   "10a",
+	Short: "Day 10, Problem A",
+	Run: func(_ *cobra.Command, _ []string) {
+		fmt.Printf("Answer: %d\n", a(challenge.FromFile()))
+	},
+}
+
+type asteroid struct {
+	x float64
+	y float64
+}
+
+func (a asteroid) distanceTo(other asteroid) float64 {
+	return math.Sqrt(math.Pow(a.x-other.x, 2) + math.Pow(a.y-other.y, 2))
+}
+
+func (a asteroid) slopeTo(other asteroid) float64 {
+	if a.y == other.y {
+		return math.Inf(1)
+	} else if a.x == other.x {
+		return 0
+	}
+
+	return math.Abs(a.x-other.x) / math.Abs(a.y-other.y)
+}
+
+func (a asteroid) canSee(other asteroid, all []asteroid) bool {
+	if a.x == other.x && a.y == other.y {
+		return false
+	}
+
+	for _, blocker := range all {
+		if (blocker.x == a.x || blocker.x == other.x) && (blocker.y == a.y || blocker.y == other.y) {
+			continue
+		} else if blocker.x < math.Min(a.x, other.x) || blocker.x > math.Max(a.x, other.x) {
+			continue
+		} else if blocker.y < math.Min(a.y, other.y) || blocker.y > math.Max(a.y, other.y) {
+			continue
+		}
+
+		if a.slopeTo(blocker) == a.slopeTo(other) {
+			return a.distanceTo(other) < a.distanceTo(blocker)
+		}
+	}
+
+	return true
+}
+
+func a(challenge *challenge.Input) int {
+	asteroids := makeMap(challenge)
+
+	best := 0
+	for _, a := range asteroids {
+		seen := 0
+		for _, other := range asteroids {
+			if a.canSee(other, asteroids) {
+				seen++
+			}
+		}
+
+		if seen > best {
+			best = seen
+		}
+	}
+
+	return best
+}
+
+func makeMap(challenge *challenge.Input) []asteroid {
+	var asteroids []asteroid
+
+	y := 0
+	for line := range challenge.Lines() {
+		for x, v := range line {
+			if v == symAsteroid {
+				asteroids = append(asteroids, asteroid{float64(x), float64(y)})
+			}
+		}
+
+		y++
+	}
+
+	return asteroids
+}

challenge/day10/a_test.go

@@ -0,0 +1,78 @@
+package day10
+
+import (
+	"strconv"
+	"testing"
+
+	"github.com/nlowe/aoc2019/challenge"
+	"github.com/stretchr/testify/require"
+)
+
+func TestA(t *testing.T) {
+	tests := []struct {
+		data     string
+		expected int
+	}{
+		{data: `.#..#
+.....
+#####
+....#
+...##`, expected: 8},
+		{data: `......#.#.
+#..#.#....
+..#######.
+.#.#.###..
+.#..#.....
+..#....#.#
+#..#....#.
+.##.#..###
+##...#..#.
+.#....####`, expected: 33},
+		{data: `#.#...#.#.
+.###....#.
+.#....#...
+##.#.#.#.#
+....#.#.#.
+.##..###.#
+..#...##..
+..##....##
+......#...
+.####.###.`, expected: 35},
+		{data: `.#..#..###
+####.###.#
+....###.#.
+..###.##.#
+##.##.#.#.
+....###..#
+..#.#..#.#
+#..#.#.###
+.##...##.#
+.....#.#..`, expected: 41},
+		{data: `.#..##.###...#######
+##.############..##.
+.#.######.########.#
+.###.#######.####.#.
+#####.##.#.##.###.##
+..#####..#.#########
+####################
+#.####....###.#.#.##
+##.#################
+#####.##.###..####..
+..######..##.#######
+####.##.####...##..#
+.#####..#.######.###
+##...#.##########...
+#.##########.#######
+.####.#.###.###.#.##
+....##.##.###..#####
+.#.#.###########.###
+#.#.#.#####.####.###
+###.##.####.##.#..##`, expected: 210},
+	}
+
+	for _, tt := range tests {
+		t.Run(strconv.Itoa(tt.expected), func(t *testing.T) {
+			require.Equal(t, tt.expected, a(challenge.FromLiteral(tt.data)))
+		})
+	}
+}

challenge/day10/input.txt

@@ -0,0 +1,43 @@
+....#.....#.#...##..........#.......#......
+.....#...####..##...#......#.........#.....
+.#.#...#..........#.....#.##.......#...#..#
+.#..#...........#..#..#.#.......####.....#.
+##..#.................#...#..........##.##.
+#..##.#...#.....##.#..#...#..#..#....#....#
+##...#.............#.#..........#...#.....#
+#.#..##.#.#..#.#...#.....#.#.............#.
+...#..##....#........#.....................
+##....###..#.#.......#...#..........#..#..#
+....#.#....##...###......#......#...#......
+.........#.#.....#..#........#..#..##..#...
+....##...#..##...#.....##.#..#....#........
+............#....######......##......#...#.
+#...........##...#.#......#....#....#......
+......#.....#.#....#...##.###.....#...#.#..
+..#.....##..........#..........#...........
+..#.#..#......#......#.....#...##.......##.
+.#..#....##......#.............#...........
+..##.#.....#.........#....###.........#..#.
+...#....#...#.#.......#...#.#.....#........
+...####........#...#....#....#........##..#
+.#...........#.................#...#...#..#
+#................#......#..#...........#..#
+..#.#.......#...........#.#......#.........
+....#............#.............#.####.#.#..
+.....##....#..#...........###........#...#.
+.#.....#...#.#...#..#..........#..#.#......
+.#.##...#........#..#...##...#...#...#.#.#.
+#.......#...#...###..#....#..#...#.........
+.....#...##...#.###.#...##..........##.###.
+..#.....#.##..#.....#..#.....#....#....#..#
+.....#.....#..............####.#.........#.
+..#..#.#..#.....#..........#..#....#....#..
+#.....#.#......##.....#...#...#.......#.#..
+..##.##...........#..........#.............
+...#..##....#...##..##......#........#....#
+.....#..........##.#.##..#....##..#........
+.#...#...#......#..#.##.....#...#.....##...
+...##.#....#...........####.#....#.#....#..
+...#....#.#..#.........#.......#..#...##...
+...##..............#......#................
+........................#....##..#........#

main.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/nlowe/aoc2019/challenge/day10"
+
 	"github.com/nlowe/aoc2019/challenge/day9"
 
 	"github.com/nlowe/aoc2019/challenge/day8"
@@ -62,6 +64,7 @@ func init() {
 		day7.A, day7.B,
 		day8.A, day8.B,
 		day9.A, day9.B,
+		day10.A,
 	)
 
 	flags := rootCmd.PersistentFlags()