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https://github.com/Crocmagnon/advent-of-code.git
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129 lines
3.5 KiB
Python
129 lines
3.5 KiB
Python
import copy
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from collections.abc import Iterable
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from functools import partial
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def main(filename: str, expected_part_1: int = None, expected_part_2: int = None):
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print(f"\n+ Running on {filename}")
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with open(filename) as f:
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data = f.read().strip().split("\n")
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data = parse_data(data)
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visible_trees = solve_part_1(data)
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solution_part_1 = len(visible_trees)
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print(f"1. Found {solution_part_1}")
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if expected_part_1:
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assert expected_part_1 == solution_part_1
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solution_part_2 = solve_part_2(data, visible_trees)
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print(f"2. Found {solution_part_2}")
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if expected_part_2:
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assert expected_part_2 == solution_part_2
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Forest = DataType = list[list[int]]
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Tree = tuple[int, int]
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def parse_data(data: list[str]) -> DataType:
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grid = []
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for row in data:
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grid.append(list(map(int, row)))
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return grid
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def solve_part_1(forest: DataType) -> set[Tree]:
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visible = set()
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forest = copy.deepcopy(forest)
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visible.update(find_visible_in_rows(forest))
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forest = map(list, zip(*forest)) # transpose grid so cols become rows
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visible.update(find_visible_in_rows(forest, swap=True))
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return visible
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def find_visible_in_rows(forest: Iterable[list[int]], swap: bool = False) -> set[Tree]:
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visible = set()
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for row, trees in enumerate(forest):
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max_height = -1
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for col, tree in enumerate(trees):
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if tree > max_height:
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max_height = tree
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visible.add(visible_tree(row, col, swap))
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max_height = -1
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for col, tree in enumerate(reversed(trees)):
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col = len(trees) - col - 1
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if tree > max_height:
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max_height = tree
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visible.add(visible_tree(row, col, swap))
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return visible
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def visible_tree(row: int, col: int, swap: bool) -> Tree:
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if swap:
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return col, row
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else:
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return row, col
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def solve_part_2(forest: DataType, visible_trees: set[Tree]) -> int:
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# Hypothesis: the tree with the highest scenic score
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# is visible from the outside.
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max_scenic_score = 0
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for tree in filter(partial(is_inside, forest=forest), visible_trees):
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scenic_score = compute_scenic_score(tree, forest)
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if scenic_score > max_scenic_score:
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max_scenic_score = scenic_score
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return max_scenic_score
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def is_border(tree: Tree, forest: DataType) -> bool:
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return 0 in tree or tree[0] == len(forest) - 1 or tree[1] == len(forest[0]) - 1
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def is_inside(tree: Tree, forest: DataType) -> bool:
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return not is_border(tree, forest)
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def compute_scenic_score(tree: Tree, forest: Forest) -> int:
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row, col = tree
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reference = forest[row][col]
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top = 0
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while row > 0:
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row -= 1
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top += 1
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visited = forest[row][col]
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if visited >= reference:
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break
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row, col = tree
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bottom = 0
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while row < len(forest) - 1:
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row += 1
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bottom += 1
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visited = forest[row][col]
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if visited >= reference:
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break
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row, col = tree
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left = 0
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while col > 0:
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col -= 1
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left += 1
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visited = forest[row][col]
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if visited >= reference:
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break
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row, col = tree
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right = 0
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while col < len(forest[0]) - 1:
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col += 1
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right += 1
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visited = forest[row][col]
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if visited >= reference:
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break
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return right * left * top * bottom
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if __name__ == "__main__":
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main("inputs/day08-test1", expected_part_1=21, expected_part_2=8)
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main("inputs/day08", expected_part_1=1690)
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