day12.py

#!/usr/bin/env python3

import numpy as np

src = open("input.txt", "r").readlines()
src = [r.strip() for r in src]

src = [[line[0], int(line[1:])] for line in src]

d2s = {
    0: "N",
    90: "E",
    180: "S",
    270: "W",
}

vec = {
    "N": np.array([0, 1]),
    "E": np.array([1, 0]),
    "S": np.array([0, -1]),
    "W": np.array([-1, 0]),
}


def make_rotation(r):
    theta = np.radians(r)
    return np.array(((np.cos(theta), -np.sin(theta)), (np.sin(theta), np.cos(theta))))


rot = {
    -90: make_rotation(-90),
    -180: make_rotation(-180),
    -270: make_rotation(-270),
    90: make_rotation(90),
    180: make_rotation(180),
    270: make_rotation(270),
}


def rotate(vec, r):
    return np.rint(vec.dot(rot[r])).astype(int)


def part1():
    pos = np.array([0, 0])
    d = 90

    for r in src:
        a, v = r

        if a == "R":
            d = (d + v) % 360

        elif a == "L":
            d = (d - v) % 360

        elif a in ("N", "E", "S", "W"):
            pos += vec[a] * v

        elif a == "F":
            pos += vec[d2s[d]] * v

    print(pos, abs(pos[0]) + abs(pos[1]))


def part2():
    pos = np.array([0, 0])
    wpos = np.array([10, 1])

    for r in src:
        a, v = r

        if a in ("N", "E", "S", "W"):
            wpos += vec[a] * v

        elif a == "R":
            wpos = rotate(wpos, v)

        elif a == "L":
            wpos = rotate(wpos, -v)

        elif a == "F":
            pos += wpos * v

    print(pos, abs(pos[0]) + abs(pos[1]))


part1()
part2()