109 lines
2.7 KiB
Python
109 lines
2.7 KiB
Python
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#!/usr/bin/env python
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import sys
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from fractions import Fraction
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from typing import Dict, List, NamedTuple, Optional
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class Point(NamedTuple):
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x: int
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y: int
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class Line(NamedTuple):
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p1: Point
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p2: Point
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def manhattan_dist(p1: Point, p2: Point = Point(0, 0)) -> int:
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dx = p2.x - p1.x if p1.x < p2.x else p1.x - p2.x
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dy = p2.y - p1.y if p1.y < p2.y else p1.y - p2.y
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return dx + dy
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def intersect(l1: Line, l2: Line) -> Optional[Point]:
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(x1, y1), (x2, y2) = l1.p1, l1.p2
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(x3, y3), (x4, y4) = l2.p1, l2.p2
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den = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4)
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if den == 0: # Parallel lines
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return None
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t = Fraction((x1 - x3) * (y3 - y4) - (y1 - y3) * (x3 - x4), den)
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if t < 0 or t > 1: # Out of l1
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return None
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u = -Fraction((x1 - x2) * (y1 - y3) - (y1 - y2) * (x1 - x3), den)
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if u < 0 or u > 1: # Out of l2
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return None
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dx = t * (x2 - x1)
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dy = t * (y2 - y1)
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assert int(dx) == dx and int(dy) == dy # Sanity checks
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ix = x1 + int(dx)
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iy = y1 + int(dy)
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return Point(ix, iy)
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def is_on(p: Point, l: Line) -> bool:
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# Assume that l is horizontal or vertical
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if l.p1.x == l.p2.x:
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if l.p1.y < l.p2.y:
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return p.x == l.p1.x and l.p1.y <= p.y <= l.p2.y
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elif l.p2.y < l.p1.y:
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return p.x == l.p1.x and l.p2.y <= p.y <= l.p1.y
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elif l.p1.y == l.p2.y:
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if l.p1.x < l.p2.x:
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return p.y == l.p1.y and l.p1.x <= p.x <= l.p2.x
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elif l.p2.x < l.p1.x:
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return p.y == l.p1.y and l.p2.x <= p.x <= l.p1.x
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assert False # Sanity checks
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def parse_line(directions: str) -> List[Line]:
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prev = Point(0, 0)
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ans = []
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for inst in directions.split(","):
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direction, length = inst[0], int(inst[1:])
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new_x, new_y = prev
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if direction == "U":
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new_y += length
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elif direction == "R":
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new_x += length
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if direction == "D":
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new_y -= length
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elif direction == "L":
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new_x -= length
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new = Point(new_x, new_y)
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ans.append(Line(prev, new))
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prev = new
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return ans
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def compute_delay(p: Point, lines: List[Line]) -> int:
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dist = 0
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for l in lines:
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if is_on(p, l):
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return dist + manhattan_dist(l.p1, p)
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dist += manhattan_dist(l.p1, l.p2)
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assert False # Sanity check
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def main() -> None:
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wire1, wire2 = tuple(parse_line(l) for l in sys.stdin)
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intersections = [intersect(l1, l2) for l1 in wire1 for l2 in wire2]
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print(
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min(
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compute_delay(x, wire1) + compute_delay(x, wire2)
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for x in intersections
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if x is not None and x != Point(0, 0) # Discard origin
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)
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)
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if __name__ == "__main__":
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main()
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