advent_of_code/2023/10/10.py

#!/usr/bin/env python
# 2023 - Advent Of Code 10

# file = 'input_example.txt'
file = 'input.txt'

# pylint: disable=consider-using-with
input_lines = [line.strip('\n') for line in open(file, encoding="utf-8")]

start_pos = (0, 0)
for y, _ in enumerate(input_lines):
    for x, tile in enumerate(_):
        #if input_lines[y][x] == 'S':
        if tile == 'S':
            start_pos = (x, y)
            print(f'\033[1m{tile}\033[0m', end='')
        else:
            print(tile, end='')
    print()

print(f'{start_pos=}')
x = start_pos[0]
y = start_pos[1]
pos_list = []
pos_list.append(start_pos)
next_pos = (-1, -1)
# find start direction
direction = -1
# direction 0: up, 1: right, 2: down, 3: left

if y > 0:  # up
    # print(f'checking {input_lines[y-1][x]=}')
    if input_lines[y-1][x] == 'F':
        next_pos = (x, y-1)
        direction = 1
    elif input_lines[y-1][x] == '7':
        next_pos = (x, y-1)
        direction = 2
    elif input_lines[y-1][x] == '|':
        next_pos = (x, y-1)
        direction = 0
if direction == -1 and x < len(input_lines[y])-1:  # right
    # print(f'checking {input_lines[y][x+1]=}')
    if input_lines[y][x+1] == 'J':
        next_pos = (x+1, y)
        direction = 0
    elif input_lines[y][x+1] == '7':
        next_pos = (x+1, y)
        direction = 2
    elif input_lines[y][x+1] == '-':
        next_pos = (x+1, y)
        direction = 1
# down
if direction == -1 and y < len(input_lines):
    # print(f'checking {input_lines[y+1][x]}')
    if input_lines[y+1][x] == 'L':
        next_pos = (x, y+1)
        direction = 1
    elif input_lines[y+1][x] == 'J':
        next_pos = (x, y+1)
        direction = 3
    elif input_lines[y+1][x] == '|':
        next_pos = (x, y+1)
        direction = 2
# left
if direction == -1 and x > 0:
    # print(f'checking {input_lines[y][x-1]}')
    if input_lines[y][x-1] == 'F':
        next_pos = (x-1, y)
        direction = 2
    elif input_lines[y][x-1] == 'L':
        next_pos = (x-1, y)
        direction = 0
    elif input_lines[y][x-1] == '-':
        next_pos = (x-1, y)
        direction = 3

print(f'{next_pos=} {direction=}')
pos_list.append(next_pos)

# loop follow directions - ends if next == 'S'
while input_lines[next_pos[1]][next_pos[0]] != 'S':
    x = next_pos[0]
    y = next_pos[1]
    if direction == 0:
        if input_lines[y - 1][x] == 'F':
            next_pos = (x, y - 1)
            direction = 1
        elif input_lines[y - 1][x] == '7':
            next_pos = (x, y - 1)
            direction = 3
        elif input_lines[y - 1][x] == '|':
            next_pos = (x, y - 1)
            direction = 0
        elif input_lines[y - 1][x] == 'S':
            break
    elif direction == 1:
        if input_lines[y][x + 1] == 'J':
            next_pos = (x + 1, y)
            direction = 0
        elif input_lines[y][x + 1] == '7':
            next_pos = (x + 1, y)
            direction = 2
        elif input_lines[y][x + 1] == '-':
            next_pos = (x + 1, y)
            direction = 1
        elif input_lines[y][x + 1] == 'S':
            break
    elif direction == 2:
        if input_lines[y + 1][x] == 'L':
            next_pos = (x, y + 1)
            direction = 1
        elif input_lines[y + 1][x] == 'J':
            next_pos = (x, y + 1)
            direction = 3
        elif input_lines[y + 1][x] == '|':
            next_pos = (x, y + 1)
            direction = 2
        elif input_lines[y + 1][x] == 'S':
            break
    elif direction == 3:
        if input_lines[y][x - 1] == 'F':
            next_pos = (x - 1, y)
            direction = 2
        elif input_lines[y][x - 1] == 'L':
            next_pos = (x - 1, y)
            direction = 0
        elif input_lines[y][x - 1] == '-':
            next_pos = (x - 1, y)
            direction = 3
        elif input_lines[y][x - 1] == 'S':
            break
    pos_list.append(next_pos)
    # print(f'{next_pos=} {direction=} {input_lines[next_pos[1]][next_pos[0]]}')

print(f'end found at {next_pos=}')
print(f'{pos_list=}')
print(f'{len(pos_list)/2=}')