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69 lines
1.6 KiB
Python
69 lines
1.6 KiB
Python
from dataclasses import dataclass
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@dataclass(frozen=True)
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class Vec2d:
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x: int
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y: int
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def __add__(self, other):
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return Vec2d(self.x + other.x, self.y + other.y)
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DIRECTIONS = (
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Vec2d(0, -1), # N
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Vec2d(1, 0), # E
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Vec2d(0, 1), # S
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Vec2d(-1, 0), # W
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)
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def in_bounds(grid, pos):
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return 0 <= pos.y < len(grid) and 0 <= pos.x < len(grid[0])
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def get_pos(grid, pos):
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return grid[pos.y][pos.x]
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def bfs(grid, start_pos):
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visited = [start_pos]
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goals = []
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while visited != []:
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current_pos = visited.pop()
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current_val = get_pos(grid, current_pos)
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if current_val == 9:
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goals.append(current_pos)
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for d in DIRECTIONS:
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next_pos = current_pos + d
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# next node can be reached if it's value is current + 1
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if in_bounds(grid, next_pos) and get_pos(grid, next_pos) == current_val + 1:
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if next_pos not in visited:
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visited.append(next_pos)
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return goals
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def main(grid):
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trailheads = []
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for y, row in enumerate(grid):
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for x, c in enumerate(row):
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if c == 0:
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trailheads.append(Vec2d(x, y))
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total = 0
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total2 = 0
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for start_pos in trailheads:
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trails = bfs(grid, start_pos)
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total += len(set(trails))
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total2 += len(trails)
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print("Part 1: ", total)
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print("Part 2: ", total2)
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if __name__ == "__main__":
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import sys
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infile = sys.argv[1] if 1 < len(sys.argv) else "example.txt"
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with open(infile) as f:
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grid = [list(map(int, list(l.rstrip()))) for l in f.readlines()]
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main(grid)
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