Add solution for Day 12

Signed-off-by: Knut Ahlers <knut@ahlers.me>

day12.go

@@ -0,0 +1,207 @@
+package aoc2019
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"math"
+	"os"
+	"regexp"
+	"strconv"
+
+	"github.com/pkg/errors"
+)
+
+type day12MoonSystem []*day12Moon
+
+func day12MoonSystemFromFile(inFile string) (day12MoonSystem, error) {
+	f, err := os.Open(inFile)
+	if err != nil {
+		return nil, errors.Wrap(err, "Unable to open inFile")
+	}
+	defer f.Close()
+
+	return day12MoonSystemFromReader(f)
+}
+
+func day12MoonSystemFromReader(r io.Reader) (day12MoonSystem, error) {
+	var moons day12MoonSystem
+
+	scanner := bufio.NewScanner(r)
+	for scanner.Scan() {
+		m, err := day12MoonFromScan(scanner.Text())
+		if err != nil {
+			return nil, errors.Wrap(err, "Unable to read input file")
+		}
+		moons = append(moons, m)
+	}
+
+	return moons, errors.Wrap(scanner.Err(), "Unable to scan file")
+}
+
+func (d day12MoonSystem) move(steps int) {
+	for i := 0; i < steps; i++ {
+		d.updateVelocity()
+		for _, m := range d {
+			m.move()
+		}
+	}
+}
+
+func (d day12MoonSystem) totalEnergy() int64 {
+	var e int64
+	for _, m := range d {
+		e += m.totalEnergy()
+	}
+	return e
+}
+
+func (d day12MoonSystem) updateVelocity() {
+	for _, affected := range d {
+		for _, affector := range d {
+			if affector == affected {
+				// Moons does not affect themselves
+				continue
+			}
+
+			if affector.PX > affected.PX {
+				affected.VX += 1
+			} else if affector.PX < affected.PX {
+				affected.VX -= 1
+			}
+
+			if affector.PY > affected.PY {
+				affected.VY += 1
+			} else if affector.PY < affected.PY {
+				affected.VY -= 1
+			}
+
+			if affector.PZ > affected.PZ {
+				affected.VZ += 1
+			} else if affector.PZ < affected.PZ {
+				affected.VZ -= 1
+			}
+		}
+	}
+}
+
+type day12Moon struct {
+	PX, PY, PZ int64
+	VX, VY, VZ int64
+}
+
+func day12MoonFromScan(scan string) (*day12Moon, error) {
+	grps := regexp.MustCompile(`^<x=([0-9-]+), y=([0-9-]+), z=([0-9-]+)>$`).FindStringSubmatch(scan)
+	if len(grps) != 4 {
+		return nil, errors.Errorf("Invalid input %q: %#v", scan, grps)
+	}
+
+	var (
+		err error
+		m   = &day12Moon{}
+	)
+
+	if m.PX, err = strconv.ParseInt(grps[1], 10, 64); err != nil {
+		return nil, errors.Wrap(err, "Invalid X")
+	}
+	if m.PY, err = strconv.ParseInt(grps[2], 10, 64); err != nil {
+		return nil, errors.Wrap(err, "Invalid Y")
+	}
+	if m.PZ, err = strconv.ParseInt(grps[3], 10, 64); err != nil {
+		return nil, errors.Wrap(err, "Invalid Z")
+	}
+
+	return m, nil
+}
+
+func (d day12Moon) String() string {
+	return fmt.Sprintf(
+		"pos=<x=%d, y=%d, z=%d>, vel=<x=%d, y=%d, z=%d>",
+		d.PX, d.PY, d.PZ,
+		d.VX, d.VY, d.VZ,
+	)
+}
+
+func (d *day12Moon) clearKinetic() { d.VX, d.VY, d.VZ = 0, 0, 0 }
+
+func (d day12Moon) eq(t *day12Moon, component int) bool {
+	switch component {
+	case 0:
+		return d.PX == t.PX && d.VX == t.VX
+	case 1:
+		return d.PY == t.PY && d.VY == t.VY
+	case 2:
+		return d.PZ == t.PZ && d.VZ == t.VZ
+	default:
+		panic("Invalid component compared")
+	}
+}
+
+func (d *day12Moon) move() {
+	d.PX += d.VX
+	d.PY += d.VY
+	d.PZ += d.VZ
+}
+
+func (d day12Moon) totalEnergy() int64 {
+	return int64((math.Abs(float64(d.PX)) + math.Abs(float64(d.PY)) + math.Abs(float64(d.PZ))) * (math.Abs(float64(d.VX)) + math.Abs(float64(d.VY)) + math.Abs(float64(d.VZ))))
+}
+
+func solveDay12Part1(inFile string) (int64, error) {
+	moons, err := day12MoonSystemFromFile(inFile)
+	if err != nil {
+		return 0, errors.Wrap(err, "Unable to read system scan")
+	}
+
+	moons.move(1000)
+
+	return moons.totalEnergy(), nil
+}
+
+func solveDay12Part2(inFile string) (int64, error) {
+	moons, err := day12MoonSystemFromFile(inFile)
+	if err != nil {
+		return 0, errors.Wrap(err, "Unable to read system scan")
+	}
+
+	initMoons, _ := day12MoonSystemFromFile(inFile)
+	var (
+		iterations [3]int64
+		completed  [3]bool
+	)
+
+	for {
+		moons.move(1)
+
+		for c := 0; c < len(completed); c++ {
+			if completed[c] {
+				continue
+			}
+
+			var matches = true
+			for i := range moons {
+				if !moons[i].eq(initMoons[i], c) {
+					matches = false
+				}
+			}
+
+			iterations[c]++
+			if matches {
+				completed[c] = true
+			}
+		}
+
+		var allComplete = true
+		for _, c := range completed {
+			if !c {
+				allComplete = false
+			}
+		}
+
+		if allComplete {
+			break
+		}
+	}
+
+	return leastCommonMultiple(leastCommonMultiple(iterations[0], iterations[1]), iterations[2]), nil
+}

day12_input.txt

@@ -0,0 +1,4 @@
+<x=-7, y=17, z=-11>
+<x=9, y=12, z=5>
+<x=-9, y=0, z=-4>
+<x=4, y=6, z=0>

day12_test.go

@@ -0,0 +1,86 @@
+package aoc2019
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestDay12MoonExample(t *testing.T) {
+	moons, err := day12MoonSystemFromReader(strings.NewReader("<x=-1, y=0, z=2>\n<x=2, y=-10, z=-7>\n<x=4, y=-8, z=8>\n<x=3, y=5, z=-1>"))
+	if err != nil {
+		t.Fatalf("Unable to parse moon system: %s", err)
+	}
+
+	if l := len(moons); l != 4 {
+		t.Fatalf("Unexpected moon count: exp=4 got=%d", l)
+	}
+
+	// Check initial state
+	for i, expStr := range []string{
+		"pos=<x=-1, y=0, z=2>, vel=<x=0, y=0, z=0>",
+		"pos=<x=2, y=-10, z=-7>, vel=<x=0, y=0, z=0>",
+		"pos=<x=4, y=-8, z=8>, vel=<x=0, y=0, z=0>",
+		"pos=<x=3, y=5, z=-1>, vel=<x=0, y=0, z=0>",
+	} {
+		if s := moons[i].String(); s != expStr {
+			t.Errorf("Unexpected moon %d: exp=%q got=%q", i, expStr, s)
+		}
+	}
+
+	// Move moons by one step
+	moons.move(1)
+
+	// Check move state
+	for i, expStr := range []string{
+		"pos=<x=2, y=-1, z=1>, vel=<x=3, y=-1, z=-1>",
+		"pos=<x=3, y=-7, z=-4>, vel=<x=1, y=3, z=3>",
+		"pos=<x=1, y=-7, z=5>, vel=<x=-3, y=1, z=-3>",
+		"pos=<x=2, y=2, z=0>, vel=<x=-1, y=-3, z=1>",
+	} {
+		if s := moons[i].String(); s != expStr {
+			t.Errorf("Unexpected moon %d: exp=%q got=%q", i, expStr, s)
+		}
+	}
+
+	// Move moons by nine more step
+	moons.move(9)
+
+	// Check move state
+	for i, expStr := range []string{
+		"pos=<x=2, y=1, z=-3>, vel=<x=-3, y=-2, z=1>",
+		"pos=<x=1, y=-8, z=0>, vel=<x=-1, y=1, z=3>",
+		"pos=<x=3, y=-6, z=1>, vel=<x=3, y=2, z=-3>",
+		"pos=<x=2, y=0, z=4>, vel=<x=1, y=-1, z=-1>",
+	} {
+		if s := moons[i].String(); s != expStr {
+			t.Errorf("Unexpected moon %d: exp=%q got=%q", i, expStr, s)
+		}
+	}
+
+	// Check energy after step 10
+	for i, expE := range []int64{
+		36, 45, 80, 18,
+	} {
+		if e := moons[i].totalEnergy(); e != expE {
+			t.Errorf("Unexpected energy on moon %d: exp=%d got=%d", i, expE, e)
+		}
+	}
+}
+
+func TestCalculateDay12_Part1(t *testing.T) {
+	count, err := solveDay12Part1("day12_input.txt")
+	if err != nil {
+		t.Fatalf("Day 12 solver failed: %s", err)
+	}
+
+	t.Logf("Solution Day 12 Part 1: %d", count)
+}
+
+func TestCalculateDay12_Part2(t *testing.T) {
+	res, err := solveDay12Part2("day12_input.txt")
+	if err != nil {
+		t.Fatalf("Day 12 solver failed: %s", err)
+	}
+
+	t.Logf("Solution Day 12 Part 2: %d", res)
+}

helpers.go

@@ -11,6 +11,10 @@ func greatestCommonDivisor(a, b int64) int64 {
 	return a
 }
 
+func leastCommonMultiple(a, b int64) int64 {
+	return a * b / greatestCommonDivisor(a, b)
+}
+
 func manhattenDistance(x1, y1, x2, y2 int) int {
 	return int(math.Abs(float64(x1-x2)) + math.Abs(float64(y1-y2)))
 }