import numpy as np
with open('data-2025-04.txt', 'r') as f:
inp = f.read().splitlines()
lists = [list(i) for i in inp]
roll = np.array(lists)Advent of Code 2025 Day 4
— Day 4: Printing Department —
There are lots of large paper rolls everywhere. We need to organise the forklifts to pick some up.
Consider your complete diagram of the paper roll locations. How many rolls of paper can be accessed by a forklift?
140 x 140 grid
Numpy for an array, I guess
summer = 0
for i in range(140):
for j in range(140):
if roll[i,j] == '@':
# make sure of our indices
a = 0 if i == 0 else 1
c = 0 if j == 0 else 1
b = 1 if i == 139 else 2
d = 1 if j == 139 else 2
# a little easier for our object
assess = roll[i-a:i+b, j-c:j+d]
# assess, remove itself
if np.count_nonzero(assess == '@') - 1 < 4:
# pick up the current roll
summer += 1
summer
# 411 too low
# 1569 1569— Part Two —
The forklifts are going to remove the rolls of paper.
Start with your original diagram. How many rolls of paper in total can be removed by the Elves and their forklifts?
We need to alter the original array to remove rolls as we go along within a while loop.
summer = 0
roll = np.array(lists)
iterations = 0
while True:
iterations += 1
if iterations > 50: break # safety
for i in range(140):
for j in range(140):
if roll[i,j] == '@':
# make sure of our indices
a = 0 if i == 0 else 1
c = 0 if j == 0 else 1
b = 1 if i == 139 else 2
d = 1 if j == 139 else 2
# a little easier for our object
assess = roll[i-a:i+b, j-c:j+d]
# assess
if np.count_nonzero(assess == '@') - 1 < 4:
# remove the current roll
roll[i,j] = '.'
summer += 1
summer
# 9280