diff --git a/2021/d15/ex2/ex2.py b/2021/d15/ex2/ex2.py new file mode 100755 index 0000000..0fa89b8 --- /dev/null +++ b/2021/d15/ex2/ex2.py @@ -0,0 +1,76 @@ +#!/usr/bin/env python + +import heapq +import itertools +import sys +from typing import Iterator, List, NamedTuple, Set, Tuple + + +class Point(NamedTuple): + x: int + y: int + + +def solve(input: List[str]) -> int: + def parse_levels() -> List[List[int]]: + levels = [[int(c) for c in line] for line in input] + width, height = len(levels), len(levels[0]) + + res = [[0 for j in range(width * 5)] for i in range(height * 5)] + + for i in range(height): + for j in range(width): + res[i][j] = levels[i][j] + + # Do first row of blocks + for i in range(height): + for j in range(width, width * 5): + res[i][j] = res[i][j - width] % 9 + 1 + + for i in range(height, height * 5): + for j in range(width * 5): + res[i][j] = res[i - height][j] % 9 + 1 + + return res + + levels = parse_levels() + + def neighbours(p: Point) -> Iterator[Point]: + for dx, dy in (-1, 0), (1, 0), (0, -1), (0, 1): + x, y = p.x + dx, p.y + dy + if x < 0 or x >= len(levels): + continue + if y < 0 or y >= len(levels[0]): + continue + yield Point(x, y) + + def djikstra(start: Point, end: Point) -> int: + # Priority queue of (distance, point) + queue = [(0, start)] + seen: Set[Point] = set() + + while len(queue) > 0: + dist, p = heapq.heappop(queue) + if p == end: + return dist + # We must have seen p with a smaller distance before + if p in seen: + continue + # First time encountering p, must be the smallest distance to it + seen.add(p) + # Add all neighbours to be visited + for n in neighbours(p): + heapq.heappush(queue, (dist + levels[n.x][n.y], n)) + + assert False # Sanity check + + return djikstra(Point(0, 0), Point(len(levels) - 1, len(levels[0]) - 1)) + + +def main() -> None: + input = [line.strip() for line in sys.stdin.readlines()] + print(solve(input)) + + +if __name__ == "__main__": + main()