advent of code 2025
day 4 part 2
+34
-19
+34
-19
4.py
+34
-19
4.py
···
1
1
import sys
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+
from typing import List, Optional, Tuple
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3
3
-
available_rolls = 0
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removed_rolls = 0
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file = '4.input' if len(sys.argv) <= 1 else sys.argv[1]
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grid = list(map(str.strip, open(file).readlines()))
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grid = list(map(list, map(str.strip, open(file).readlines())))
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def check_occupied(y: int, x: int) -> int:
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def check_occupied(y: int, x: int) -> Optional[Tuple[int, int]]:
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try:
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return x >= 0 and y >= 0 and grid[y][x] == "@"
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except IndexError:
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return False
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if x >= 0 and y >= 0 and grid[y][x] == "@":
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return (y, x)
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except IndexError: pass
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return None
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def compute_adj(y: int, x: int) -> List[Optional[Tuple[int, int]]]:
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return [
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check_occupied(y-1, x-1), check_occupied(y-1, x), check_occupied(y-1, x+1),
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check_occupied(y, x-1), check_occupied(y, x+1),
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check_occupied(y+1, x-1), check_occupied(y+1, x), check_occupied(y+1, x+1)
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]
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def search_removable() -> List[Tuple[int, int]]:
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removable = []
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for y in range(len(grid)):
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for x in range(len(grid[y])):
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if grid[y][x] != "@": continue
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adj = compute_adj(y, x)
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if sum(map(bool, adj)) < 4:
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removable.append((y, x))
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return removable
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for y in range(len(grid)):
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row = grid[y]
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for x in range(len(row)):
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if row[x] != "@": continue
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adj = sum([
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check_occupied(y-1, x-1), check_occupied(y-1, x), check_occupied(y-1, x+1),
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check_occupied(y, x-1), check_occupied(y, x+1),
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check_occupied(y+1, x-1), check_occupied(y+1, x), check_occupied(y+1, x+1)
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])
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if adj < 4:
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available_rolls += 1
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removable = search_removable()
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print(f'p1: {len(removable)}')
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+
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while len(removable):
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for (y, x) in removable:
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grid[y][x] = "."
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removed_rolls += 1
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removable = search_removable()
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40
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print(f'p1: {available_rolls}')
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# print(f'p2: {}')
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print(f'p2: {removed_rolls}')