24 lines
620 B
Python
24 lines
620 B
Python
def queens(n):
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a = list(range(n))
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up = [True]*(2*n - 1)
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down = [True]*(2*n - 1)
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def sub(i):
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if i == n:
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yield tuple(a)
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else:
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for k in range(i, n):
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j = a[k]
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p = i + j
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q = i - j + n - 1
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if up[p] and down[q]:
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up[p] = down[q] = False
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a[i], a[k] = a[k], a[i]
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yield from sub(i + 1)
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up[p] = down[q] = True
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a[i], a[k] = a[k], a[i]
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yield from sub(0)
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#Count solutions for n=8:
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sum(1 for p in queens(8))
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92
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