55 lines
1.4 KiB
Python
Executable file
55 lines
1.4 KiB
Python
Executable file
#!/usr/bin/env python
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import heapq
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import sys
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from typing import Iterator, List, NamedTuple, Set
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class Point(NamedTuple):
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x: int
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y: int
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def solve(input: List[str]) -> int:
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levels = [[int(c) for c in line] for line in input]
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def neighbours(p: Point) -> Iterator[Point]:
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for dx, dy in (-1, 0), (1, 0), (0, -1), (0, 1):
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x, y = p.x + dx, p.y + dy
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if x < 0 or x >= len(levels):
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continue
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if y < 0 or y >= len(levels[0]):
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continue
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yield Point(x, y)
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def djikstra(start: Point, end: Point) -> int:
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# Priority queue of (distance, point)
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queue = [(0, start)]
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seen: Set[Point] = set()
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while len(queue) > 0:
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dist, p = heapq.heappop(queue)
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if p == end:
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return dist
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# We must have seen p with a smaller distance before
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if p in seen:
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continue
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# First time encountering p, must be the smallest distance to it
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seen.add(p)
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# Add all neighbours to be visited
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for n in neighbours(p):
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heapq.heappush(queue, (dist + levels[n.x][n.y], n))
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assert False # Sanity check
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return djikstra(Point(0, 0), Point(len(levels) - 1, len(levels[0]) - 1))
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def main() -> None:
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input = [line.strip() for line in sys.stdin.readlines()]
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print(solve(input))
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if __name__ == "__main__":
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main()
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