152 lines
4.2 KiB
Python
152 lines
4.2 KiB
Python
import lib
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import math
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EXAMPLE = """
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Sensor at x=2, y=18: closest beacon is at x=-2, y=15
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Sensor at x=9, y=16: closest beacon is at x=10, y=16
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Sensor at x=13, y=2: closest beacon is at x=15, y=3
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Sensor at x=12, y=14: closest beacon is at x=10, y=16
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Sensor at x=10, y=20: closest beacon is at x=10, y=16
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Sensor at x=14, y=17: closest beacon is at x=10, y=16
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Sensor at x=8, y=7: closest beacon is at x=2, y=10
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Sensor at x=2, y=0: closest beacon is at x=2, y=10
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Sensor at x=0, y=11: closest beacon is at x=2, y=10
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Sensor at x=20, y=14: closest beacon is at x=25, y=17
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Sensor at x=17, y=20: closest beacon is at x=21, y=22
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Sensor at x=16, y=7: closest beacon is at x=15, y=3
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Sensor at x=14, y=3: closest beacon is at x=15, y=3
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Sensor at x=20, y=1: closest beacon is at x=15, y=3
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"""
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def unify_ranges(ranges):
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# aaaaaaaaaaa
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# bbbb
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#
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# aaa
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# bbb
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#
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# aaa
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# bbb
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ranges = sorted(ranges)
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while True:
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for i in range(len(ranges) - 1):
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a, b = ranges[i], ranges[i + 1]
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if a == b:
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del ranges[i]
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break
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elif a[0] == b[0]:
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ranges[i] = (a[0], max(a[1], b[1]))
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del ranges[i + 1]
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break
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elif a[1] == b[1]:
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ranges[i] = (min(a[0], b[0]), b[1])
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del ranges[i + 1]
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break
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elif a[0] < b[0] and a[1] > b[1]:
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del ranges[i + 1]
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break
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elif a[0] > b[0] and a[1] < b[1]:
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del ranges[i]
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break
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elif a[1] < b[0]:
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pass
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elif a[0] <= b[1] and a[1] >= b[0]:
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ranges[i] = (a[0], b[1])
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del ranges[i + 1]
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break
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else:
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raise Exception("uhoh", a, b)
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else:
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return ranges
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return ranges
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def mdist(dx, dy):
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return abs(dx) + abs(dy)
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def xdist(dm, dy):
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x = dm - abs(dy)
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if x <= 0:
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return 0
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return x
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def solve(lines: list[str], yt):
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sensors = []
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bacons = set()
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for (i, line) in enumerate(lines):
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digits = lib.str_to_ints(line)
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sx, sy, bx, by = digits
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sm = mdist(bx - sx, by - sy)
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sensors.append([sx, sy, sm])
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bacons.add((bx, by))
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ranges = []
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for (sx, sy, sm) in sensors:
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x_range = xdist(sm, yt - sy)
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if x_range == 0:
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continue
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r = (sx - x_range, sx + x_range)
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# print(f"{sx=} {sy=} {r=}")
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ranges.append(r)
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ranges = unify_ranges(ranges)
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r = 0
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for (a, b) in ranges:
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r += b - a + 1
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for (bx, by) in list(bacons):
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if by == yt and bx >= a and bx <= b:
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r -= 1
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# 140:00 I don't know what a Manhattan distance is.
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return r
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def solve2(lines: list[str], xymax):
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sensors = []
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bacons = set()
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for (i, line) in enumerate(lines):
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digits = lib.str_to_ints(line)
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sx, sy, bx, by = digits
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sm = mdist(bx - sx, by - sy)
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sensors.append([sx, sy, sm])
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bacons.add((bx, by))
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finds = []
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for yt in range(0, xymax):
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ranges = []
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for (sx, sy, sm) in sensors:
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x_range = xdist(sm, yt - sy)
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if x_range == 0:
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continue
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r = (sx - x_range, sx + x_range)
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ranges.append(r)
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ranges = unify_ranges(ranges)
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if ranges[0][0] > 0:
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raise Exception("Bacon at 0.")
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elif ranges[-1][-1] < xymax:
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raise Exception("Bacon at xymax.")
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for i in range(len(ranges) - 1):
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if ranges[i + 1][0] - ranges[i][1] > 1:
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finds.append((ranges[i][1] + 1, yt))
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if len(finds) != 1:
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raise Exception("TOO MANY FINDS")
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else:
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x, y = finds[0]
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return x * 4000000 + y
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# 10:00
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def main():
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lines = lib.str_to_lines_no_empty(EXAMPLE)
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print("Example 1:", solve(lines, 10))
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lines = lib.str_to_lines_no_empty(open("i15.txt").read())
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print("Solution 1:", solve(lines, 2000000))
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lines = lib.str_to_lines_no_empty(EXAMPLE)
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print("Example 2:", solve2(lines, 20))
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lines = lib.str_to_lines_no_empty(open("i15.txt").read())
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print("Solution 2:", solve2(lines, 4000000))
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if __name__ == "__main__":
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main()
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