Day 22 - Advent of Code 2022

""" day_22_01.py """

# usage: python3 day_22_01.py < input


import sys


def parse(data):
    """ extract board and path to follow """
    rows = [list(row) for row in data.splitlines()]

    directions = []
    steps = ''
    for i in rows[-1]:
        if i in '0123456789':
            steps = steps + i
        else:
            directions.extend([int(steps), i])
            steps = ''
    directions.append(int(steps))
    return rows[:-2], directions


def start(data):
    """ find first '.' from top-left of board """
    return data[0].index('.'), 0


def get(pos, data):
    """ retrieve value ignoring out of range """
    try:
        return data[pos[1]][pos[0]]
    except IndexError:
        return ' '


board, path = parse(sys.stdin.read())
width, height = max([len(i) for i in board]), len(board)

deltas = {0: (1, 0), 1: (0, 1), 2: (-1, 0), 3: (0, -1)}
facing = 0
x, y = start(board)

for step in path:
    if step == 'L':
        facing = (facing - 1) % 4
    elif step == 'R':
        facing = (facing + 1) % 4
    else:
        dx, dy = deltas[facing]
        for _ in range(step):
            while True:
                if get((x, y), board) != ' ':
                    x0, y0 = x, y
                x1, y1 = (x + dx) % width, (y + dy) % height
                if get((x1, y1), board) == ' ':
                    x, y = x1, y1
                    continue
                break
            if get((x1, y1), board) == '.':
                x, y = x1, y1
                continue
            x, y = x0, y0
            break
print(1000 * (y + 1) + 4 * (x + 1) + facing)

# standby ...