24 lines
581 B
Python
24 lines
581 B
Python
def queens(n: int):
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def sub(i: int):
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if i < n:
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for k in range(i, n):
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j = a[k]
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if b[i + j] and c[i - j]:
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a[i], a[k] = a[k], a[i]
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b[i + j] = c[i - j] = False
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yield from sub(i + 1)
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b[i + j] = c[i - j] = True
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a[i], a[k] = a[k], a[i]
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else:
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yield a
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a = list(range(n))
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b = [True] * (2 * n - 1)
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c = [True] * (2 * n - 1)
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yield from sub(0)
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sum(1 for solution in queens(8)) # count solutions
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92
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