diff --git a/2019/d03/ex2/ex2.py b/2019/d03/ex2/ex2.py new file mode 100755 index 0000000..077f2e3 --- /dev/null +++ b/2019/d03/ex2/ex2.py @@ -0,0 +1,108 @@ +#!/usr/bin/env python + +import sys +from fractions import Fraction +from typing import List, NamedTuple, Optional + + +class Point(NamedTuple): + x: int + y: int + + +class Line(NamedTuple): + p1: Point + p2: Point + + +def manhattan_dist(p1: Point, p2: Point = Point(0, 0)) -> int: + dx = p2.x - p1.x if p1.x < p2.x else p1.x - p2.x + dy = p2.y - p1.y if p1.y < p2.y else p1.y - p2.y + return dx + dy + + +def intersect(l1: Line, l2: Line) -> Optional[Point]: + (x1, y1), (x2, y2) = l1.p1, l1.p2 + (x3, y3), (x4, y4) = l2.p1, l2.p2 + + den = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4) + + if den == 0: # Parallel lines + return None + + t = Fraction((x1 - x3) * (y3 - y4) - (y1 - y3) * (x3 - x4), den) + if t < 0 or t > 1: # Out of l1 + return None + + u = -Fraction((x1 - x2) * (y1 - y3) - (y1 - y2) * (x1 - x3), den) + if u < 0 or u > 1: # Out of l2 + return None + + dx = t * (x2 - x1) + dy = t * (y2 - y1) + + assert int(dx) == dx and int(dy) == dy # Sanity checks + + ix = x1 + int(dx) + iy = y1 + int(dy) + return Point(ix, iy) + + +def is_on(p: Point, l: Line) -> bool: + # Assume that l is horizontal or vertical + if l.p1.x == l.p2.x: + if l.p1.y < l.p2.y: + return p.x == l.p1.x and l.p1.y <= p.y <= l.p2.y + elif l.p2.y < l.p1.y: + return p.x == l.p1.x and l.p2.y <= p.y <= l.p1.y + elif l.p1.y == l.p2.y: + if l.p1.x < l.p2.x: + return p.y == l.p1.y and l.p1.x <= p.x <= l.p2.x + elif l.p2.x < l.p1.x: + return p.y == l.p1.y and l.p2.x <= p.x <= l.p1.x + assert False # Sanity checks + + +def parse_line(directions: str) -> List[Line]: + prev = Point(0, 0) + ans = [] + for inst in directions.split(","): + direction, length = inst[0], int(inst[1:]) + new_x, new_y = prev + if direction == "U": + new_y += length + elif direction == "R": + new_x += length + if direction == "D": + new_y -= length + elif direction == "L": + new_x -= length + new = Point(new_x, new_y) + ans.append(Line(prev, new)) + prev = new + return ans + + +def compute_delay(p: Point, lines: List[Line]) -> int: + dist = 0 + for l in lines: + if is_on(p, l): + return dist + manhattan_dist(l.p1, p) + dist += manhattan_dist(l.p1, l.p2) + assert False # Sanity check + + +def main() -> None: + wire1, wire2 = tuple(parse_line(l) for l in sys.stdin) + intersections = [intersect(l1, l2) for l1 in wire1 for l2 in wire2] + print( + min( + compute_delay(x, wire1) + compute_delay(x, wire2) + for x in intersections + if x is not None and x != Point(0, 0) # Discard origin + ) + ) + + +if __name__ == "__main__": + main()