Solution to Advent of Code 2020 Day 12 Part 1

AOC_2020_Day12_Part1.js

const { parseInputFile } = require('../utils/parser');

const Dir = {
    NORTH: 0,
    EAST: 90,
    SOUTH: 180,
    WEST: 270
};

const inputSteps = parseInputFile('day12-input.txt', /^(\w)(\d+)$/gm)
    .map(([, action, num]) => ({
        action,
        amount: parseInt(num)
    }));

// +east -west
let x = 0;

// +north -south
let y = 0;

// 0north 90east 180south 270 west
let dir = Dir.EAST;

function adjustDir(amount) {
    dir += amount;

    while (dir > 360) {
        dir -= 360;
    }

    while (dir < 0) {
        dir += 360;
    }

    if (dir === 360) {
        dir = 0;
    }
}


for (const step of inputSteps) {
    switch (step.action) {
        case 'N':
            y += step.amount;
            break;
        case 'S':
            y -= step.amount;
            break;
        case 'E':
            x += step.amount;
            break;
        case 'W':
            x -= step.amount;
            break;
        case 'L':
            adjustDir(-1 * step.amount);
            break;
        case 'R':
            adjustDir(step.amount);
            break;
        case 'F':
            switch (dir) {
                case Dir.NORTH:
                    y += step.amount;
                    break;
                case Dir.SOUTH:
                    y -= step.amount;
                    break;
                case Dir.EAST:
                    x += step.amount;
                    break;
                case Dir.WEST:
                    x -= step.amount;
                    break;
                default:
                    throw new Error(`Unknown direction: ${ dir }`);
            }
            break;
        default:
            throw new Error('Invalid step');
    }
}

const manhattanDistance = Math.abs(x) + Math.abs(y);
console.log(`Part 1: Manhattan distance of trip is ${ manhattanDistance }`);