Day 12: Part 1 and 2

Signed-off-by: James Griffin <james@unsupervised.ca>

twelve/day_twelve.go

@@ -0,0 +1,188 @@
+package twelve
+
+import (
+	"bufio"
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+)
+
+type instruction struct {
+	action string
+	value  int
+}
+
+type waypoint struct {
+	x, y int
+}
+
+type boat struct {
+	orientation int
+	orders      []instruction
+	x, y        int
+	waypoint    waypoint
+}
+
+func (b *boat) load(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		amount, err := strconv.Atoi(scanner.Text()[1:])
+		if err != nil {
+			return err
+		}
+
+		b.orders = append(b.orders, instruction{
+			action: scanner.Text()[:1],
+			value:  amount,
+		})
+	}
+
+	return nil
+}
+
+func loadBoat(filename string) (*boat, error) {
+	b := &boat{
+		waypoint: waypoint{
+			x: 10,
+			y: 1,
+		},
+	}
+
+	err := b.load(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	return b, nil
+}
+
+func (b *boat) advance(distance int) {
+	if b.orientation > 315 || b.orientation < 45 {
+		b.x += distance
+		return
+	}
+
+	if b.orientation > 45 && b.orientation < 135 {
+		b.y += distance
+		return
+	}
+
+	if b.orientation > 135 && b.orientation < 225 {
+		b.x -= distance
+	}
+
+	if b.orientation > 225 && b.orientation < 315 {
+		b.y -= distance
+	}
+}
+
+func (b *boat) navigate() int {
+	for _, o := range b.orders {
+		switch o.action {
+		case "F":
+			b.advance(o.value)
+		case "N":
+			b.y += o.value
+		case "S":
+			b.y -= o.value
+		case "E":
+			b.x += o.value
+		case "W":
+			b.x -= o.value
+		case "L":
+			b.orientation += o.value
+		case "R":
+			b.orientation -= o.value
+		}
+
+		for b.orientation >= 360 {
+			b.orientation -= 360
+		}
+
+		for b.orientation < 0 {
+			b.orientation += 360
+		}
+	}
+
+	return int(math.Abs(float64(b.x))) + int(math.Abs(float64(b.y)))
+}
+
+func (b *boat) rotate(degrees int) {
+	newX, newY := b.waypoint.x, b.waypoint.y
+
+	if degrees == 90 || degrees == -270 {
+		newX = b.waypoint.y * -1
+		newY = b.waypoint.x
+	}
+
+	if degrees == 180 || degrees == -180 {
+		newX = b.waypoint.x * -1
+		newY = b.waypoint.y * -1
+	}
+
+	if degrees == 270 || degrees == -90 {
+		newX = b.waypoint.y
+		newY = b.waypoint.x * -1
+	}
+
+	b.waypoint.x = newX
+	b.waypoint.y = newY
+}
+
+func (b *boat) waypointNavigate() int {
+	for _, o := range b.orders {
+		switch o.action {
+		case "F":
+			b.x += o.value * b.waypoint.x
+			b.y += o.value * b.waypoint.y
+		case "N":
+			b.waypoint.y += o.value
+		case "S":
+			b.waypoint.y -= o.value
+		case "E":
+			b.waypoint.x += o.value
+		case "W":
+			b.waypoint.x -= o.value
+		case "L":
+			b.rotate(o.value)
+		case "R":
+			b.rotate(o.value * -1)
+		}
+
+		for b.orientation >= 360 {
+			b.orientation -= 360
+		}
+
+		for b.orientation < 0 {
+			b.orientation += 360
+		}
+	}
+	return int(math.Abs(float64(b.x))) + int(math.Abs(float64(b.y)))
+}
+
+// PartOne What is the Manhatten distance that the boat travelled?
+func PartOne() string {
+	b, err := loadBoat("twelve/input.txt")
+	if err != nil {
+		return err.Error()
+	}
+
+	return fmt.Sprintf("The boat travelled a manhattan distance of %d", b.navigate())
+}
+
+// PartTwo What is the Manhatten distance that the boat travelled using a waypoint?
+func PartTwo() string {
+	b, err := loadBoat("twelve/input.txt")
+	if err != nil {
+		return err.Error()
+	}
+
+	return fmt.Sprintf("The boat travelled a manhattan distance of %d using a waypoint", b.waypointNavigate())
+}