My Advent of Code solutions in Python.
kevinyap.ca/2019/12/going-fast-in-advent-of-code/
advent-of-code
python
Add solution for 2019/10
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2019/day10.py
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2019/day10.py
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import math
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import fileinput
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from collections import deque, defaultdict
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def dist(x, y):
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return (((x[0] - y[0]) ** 2) + ((x[1] - y[1]) ** 2)) ** 0.5
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def angle(a, b):
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return math.atan2(a[1] - b[1], a[0] - b[0])
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EPS = 1e-6
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# Read problem input
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grid = []
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asteroids = set()
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for y, line in enumerate(fileinput.input()):
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for x, c in enumerate(line.strip()):
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if c == '#':
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asteroids.add((x, y))
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grid.append([c == '#' for c in line.strip()])
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width = len(grid[0])
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height = len(grid)
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# Part 1
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detections = {}
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for y in range(height):
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for x in range(width):
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if not grid[y][x]:
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continue
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p = (x, y)
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count = 0
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seen_angles = set()
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for other in sorted(asteroids, key=lambda a: dist(p, a))[1:]:
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if angle(p, other) not in seen_angles:
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seen_angles.add(angle(p, other))
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count += 1
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detections[x, y] = count
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station, num = max(detections.items(), key=lambda x: x[1])
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print "Number of detections:", num
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# Part 2
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asteroids.remove(station)
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# Construct a circular list that is sorted by increasing angle,
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# and contains sorted lists of the asteroids at that angle from
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# the station (going from furthest to closest). We rotate in the
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# positive-radian direction as a hack, since the y-axis coordinates
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# actually increase going downwards (as opposed to upwards).
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by_angles = defaultdict(list)
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for a in asteroids:
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by_angles[angle(station, a)].append(a)
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for k, v in by_angles.items():
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v.sort(key=lambda a: -dist(station, a))
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queue = deque(sorted(by_angles.items()))
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# Rotate the queue to the starting angle
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start = math.pi / 2
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while abs(queue[0][0] - start) > EPS:
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queue.rotate(-1)
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# Iterate through the circular list, vaporizing the closest asteroid
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# at that angle, then moving to the next angle in the rotation.
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for i in range(200):
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at_angle = queue[0][1]
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vaporized = at_angle.pop()
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if not at_angle:
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queue.popleft()
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else:
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queue.rotate(-1)
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print "200th asteroid checksum:", vaporized[0] * 100 + vaporized[1]
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2019/inputs/10.txt
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2019/inputs/10.txt
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.###..#######..####..##...#
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########.#.###...###.#....#
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###..#...#######...#..####.
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.##.#.....#....##.#.#.....#
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###.#######.###..##......#.
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#..###..###.##.#.#####....#
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#.##..###....#####...##.##.
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####.##..#...#####.#..###.#
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#..#....####.####.###.#.###
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#..#..#....###...#####..#..
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##...####.######....#.####.
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####.##...###.####..##....#
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#.#..#.###.#.##.####..#...#
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..##..##....#.#..##..#.#..#
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##.##.#..######.#..#..####.
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#.....#####.##........#####
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###.#.#######..#.#.##..#..#
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###...#..#.#..##.##..#####.
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.##.#..#...#####.###.##.##.
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...#.#.######.#####.#.####.
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#..##..###...###.#.#..#.#.#
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.#..#.#......#.###...###..#
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#.##.#.#..#.#......#..#..##
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.##.##.##.#...##.##.##.#..#
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#.###.#.#...##..#####.###.#
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#.####.#..#.#.##.######.#..
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.#.#####.##...#...#.##...#.