aoc-2022-day5.py

import re

def partN(input_data, one_at_a_time):

    step = 4
    instructions = []
    stack_data, instruction_data = input_data.split('\n\n')
    cols = int(stack_data.strip().split()[-1]) # ugh?
    stacks = [''] * cols
    stacks_data_lines = list(reversed(stack_data.split('\n')[:-1]))

    col_indexes = range(1, cols * step, step) # range(1, 10, 4)

    for line in stacks_data_lines:
        for ix, col in enumerate(col_indexes):
            try:
                char = line[col]
            except:
                pass
            else:
                if char.strip():
                    stacks[ix] += char

    for instruction in instruction_data.split('\n'):
        # ugh?
        num = int(instruction.split()[1])
        from_ = int(instruction.split()[3])-1
        to = int(instruction.split()[5])-1
        if one_at_a_time:
            stacks[to] += ''.join(reversed(stacks[from_][-num:]))
        else:
            stacks[to] += stacks[from_][-num:]

        stacks[from_] = stacks[from_][:-num]
    
    return ''.join([s[-1] for s in stacks])


if __name__ == '__main__':

    with open('./input.txt') as f:
        inp = f.read()

    print(partN(inp, True))
    print(partN(inp, False))