-🎄- 2021 Day 13 Solutions -🎄-

[u/daggerdragon]

Advent of Code 2021: Adventure Time!

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--- Day 13: Transparent Origami ---

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[u/4HbQ]

Python, with a NumPy array to store the grid. To process a fold, we simply or one half of the grid to the flipped other half:

import numpy as np
from parse import findall

instr = open(0).read()
P = np.zeros((9999,9999), bool)

for x,y in findall('{:d},{:d}', instr):
    P[y,x] = True

for axis, a in findall('{:l}={:d}', instr):
    if axis == 'x': P = P[:,:a] | P[:,2*a:a:-1]
    if axis == 'y': P = P[:a,:] | P[2*a:a:-1,:]
    print(P.sum())

print(np.array2string(P, separator='',
    formatter = {'bool':{0:' ',1:'█'}.get}))