My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add 2025/04
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+37
2025/day04.py
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2025/day04.py
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import fileinput
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from copy import deepcopy
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from utils import Point, DIRS_8
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# Read problem input.
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BOARD = {}
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for y, line in enumerate(fileinput.input()):
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for x, c in enumerate(line.strip()):
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BOARD[Point(x, y)] = c
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# Solve problem.
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TOTAL_PAPER = 0
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while True:
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new_board = deepcopy(BOARD)
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removed = 0
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for p, c in BOARD.items():
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if c != '@':
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continue
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adjacent = sum(BOARD.get(p + d) == '@' for d in DIRS_8)
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if adjacent < 4:
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new_board[p] = '.'
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removed += 1
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if TOTAL_PAPER == 0:
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print("Part 1:", removed)
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TOTAL_PAPER += removed
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BOARD = new_board
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if removed == 0:
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break
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print("Part 2:", TOTAL_PAPER)
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