aoc2020/day12/solve2.go

package day12

import (
	"log"
)

type Waypoint struct {
	North, East int
}

type State2 struct {
	Waypoint    Waypoint
	North, East int
}

func Solve2() {
	state := State2{
		Waypoint: Waypoint{North: 1, East: 10},
		North:    0,
		East:     0,
	}

	for _, row := range rows {
		switch row.Char {
		case "N":
			state.Waypoint.North += row.Arg

		case "S":
			state.Waypoint.North -= row.Arg

		case "E":
			state.Waypoint.East += row.Arg

		case "W":
			state.Waypoint.East -= row.Arg

		case "R":
			switch row.Arg % 360 {
			case 180:
				state.Waypoint.East *= -1
				state.Waypoint.North *= -1

			case 90:
				// Turn right a bit
				n := state.Waypoint.East * -1
				e := state.Waypoint.North

				state.Waypoint.North = n
				state.Waypoint.East = e

			case 270:
				// Turn left a bit
				n := state.Waypoint.East
				e := state.Waypoint.North * -1

				state.Waypoint.North = n
				state.Waypoint.East = e
			}

		case "L":
			switch row.Arg % 360 {
			case 180:
				state.Waypoint.East *= -1
				state.Waypoint.North *= -1

			case 90:
				// Turn right a bit
				n := state.Waypoint.East
				e := state.Waypoint.North * -1

				state.Waypoint.North = n
				state.Waypoint.East = e

			case 270:
				// Turn left a bit
				n := state.Waypoint.East * -1
				e := state.Waypoint.North

				state.Waypoint.North = n
				state.Waypoint.East = e
			}

		case "F":
			state.North += state.Waypoint.North * row.Arg
			state.East += state.Waypoint.East * row.Arg
		}
	}

	if state.East < 0 {
		state.East *= -1
	}

	if state.North < 0 {
		state.North *= -1
	}

	log.Printf("2020-12-12.02: Answer: %d\n", state.North+state.East)
}