2020aoc/Day12Part2.java

package dev.forstenlechner.aoc;

import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Day12Part2 {

    public static void main(String[] args) throws Exception {
        new Day12Part2().solve();
    }

    private enum Orientation {
        N(0), E(1), S(2), W(3);

        int value;
        Orientation(int value) {
            this.value = value;
        }

        int getValue() {
            return value;
        }

        static Orientation from(int value) {
            return switch (value) {
                case 1 -> E;
                case 2 -> S;
                case 3 -> W;
                default -> N;
            };
        }
    }

    private enum Instruction {
        N {
            @Override
            Navigation move(Navigation current, int value) {
                return new Navigation(current.ship(), new WayPoint(current.waypoint().east(), current.waypoint().north() + value));
            }
        },
        S {
            @Override
            Navigation move(Navigation current, int value) {
                return new Navigation(current.ship(), new WayPoint(current.waypoint().east(), current.waypoint().north() - value));
            }
        },
        E {
            @Override
            Navigation move(Navigation current, int value) {
                return new Navigation(current.ship(), new WayPoint(current.waypoint().east() + value, current.waypoint().north()));
            }
        },
        W {
            @Override
            Navigation move(Navigation current, int value) {
                return new Navigation(current.ship(), new WayPoint(current.waypoint().east() - value, current.waypoint().north()));
            }
        },
        L {
            @Override
            Navigation move(Navigation current, int value) {
                WayPoint currentWayPoint = current.waypoint();
                WayPoint newWayPoint = switch (value) {
                    case 90 -> new WayPoint(-currentWayPoint.north, currentWayPoint.east);
                    case 180 -> new WayPoint(-currentWayPoint.east, -currentWayPoint.north);
                    case 270 -> new WayPoint(currentWayPoint.north, -currentWayPoint.east);
                    default -> {throw new IllegalArgumentException();}
                };

                return new Navigation(current.ship(), newWayPoint);
            }
        },
        R {
            @Override
            Navigation move(Navigation current, int value) {
                WayPoint currentWayPoint = current.waypoint();
                WayPoint newWayPoint = switch (value) {
                    case 90 -> new WayPoint(currentWayPoint.north, -currentWayPoint.east);
                    case 180 -> new WayPoint(-currentWayPoint.east, -currentWayPoint.north);
                    case 270 -> new WayPoint(-currentWayPoint.north, currentWayPoint.east);
                    default -> {throw new IllegalArgumentException();}
                };

                return new Navigation(current.ship(), newWayPoint);
            }
        },
        F {
            @Override
            Navigation move(Navigation current, int value) {
                Location shipLocation = current.ship();
                WayPoint wayPoint = current.waypoint();
                Location newLocation = new Location(shipLocation.east + (wayPoint.east * value), shipLocation.north + (wayPoint.north * value));
                return new Navigation(newLocation, wayPoint);
            }
        };

        abstract Navigation move(Navigation navigation, int value);
    }

    private record NavigationInstruction(Instruction ins, int value) {};

    private record Location(int east, int north) {};

    private record WayPoint(int east, int north) {};

    private record Navigation(Location ship, WayPoint waypoint) {};

    private void solve() throws Exception {
        Stream<String> lines = Files.lines(Paths.get("day12/input"));

        List<NavigationInstruction> navigationInstructions = lines
                .map(l -> new NavigationInstruction(Instruction.valueOf(l.substring(0, 1)), Integer.parseInt(l.substring(1))))
                .collect(Collectors.toList());

        Navigation starting = new Navigation(new Location(0, 0), new WayPoint(10, 1));
        Navigation result = navigationInstructions.stream().reduce(starting, (l, n) -> {
            return n.ins().move(l, n.value());
        }, (l1, l2) -> l1);

        System.out.println(Math.abs(result.ship().east()) + Math.abs(result.ship().north()));

    }
}