Anders Englöf Ytterström
b8409db06c
Flood fill was too expensive, so I tried solving it with ray casting. I believe it is the 2nd or 3rd time during 11 runs where it has been requested. wip wip
84 lines
2 KiB
Python
84 lines
2 KiB
Python
from math import inf
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from itertools import combinations
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from output import ints
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def solve(data):
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p1 = 0
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p2 = 0
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A = [tuple(ints(pos)) for pos in data.splitlines()]
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T = inf
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R = 0
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B = 0
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L = inf
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for r, c in A:
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T = min(r, T)
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R = max(c, R)
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B = max(r, B)
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L = min(c, L)
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S = A[0]
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V = set()
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W = set()
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while True:
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V.add(S)
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W.add(S)
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y, x = S
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he = [(r, c) for r, c in A if r == y and (r, c) not in V]
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ve = [(r, c) for r, c in A if c == x and (r, c) not in V]
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if not he and not ve:
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E = A[0]
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elif he and ve:
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E = min(min(he), min(ve))
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elif he and not ve:
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E = min(he)
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else:
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E = min(ve)
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y2, x2 = E
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for r in range(min(y, y2), max(y, y2) + 1):
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for c in range(min(x, x2), max(x, x2) + 1):
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W.add((r, c))
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if E == A[0]:
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break
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S = E
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V = V | W
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for a, b in combinations(A, r=2):
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y1, x1 = a
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y2, x2 = b
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x = abs(x1 - x2) + 1
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y = abs(y1 - y2) + 1
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p1 = max(p1, x * y)
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if _within(W, a, b, T, R, B, L):
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p2 = max(p2, max(p2, x * y))
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return p1, p2
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def _within(W, a, b, T, R, B, L):
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y1, x1 = a
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y2, x2 = b
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for r in range(min(y1, y2) + 1, max(y1, y2)):
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for c in range(min(x1, x2) + 1, max(x1, x2)):
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if (r, c) in W:
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continue
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for s, e in [(T, r), (r, B)]:
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z = sum((nr, c) in W for nr in range(s, e))
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if z and z % 2 == 0:
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return False
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for s, e in [(L, c), (c, R)]:
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z = sum((r, nc) in W for nc in range(s, e))
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if z and z % 2 == 0:
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return False
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return True
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if __name__ == "__main__":
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with open("./input/09.txt", "r") as f:
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inp = f.read().strip()
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p1, p2 = solve(inp)
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print(p1)
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print(p2)
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assert p1 == 4749838800
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assert p2 == 1624057680
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