68 lines
1.9 KiB
Python
68 lines
1.9 KiB
Python
# Source: https://github.com/python/pyperformance
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# License: MIT
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# Simple, brute-force N-Queens solver.
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# author: collinwinter@google.com (Collin Winter)
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# n_queens function: Copyright 2009 Raymond Hettinger
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# Pure-Python implementation of itertools.permutations().
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def permutations(iterable, r=None):
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"""permutations(range(3), 2) --> (0,1) (0,2) (1,0) (1,2) (2,0) (2,1)"""
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pool = tuple(iterable)
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n = len(pool)
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if r is None:
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r = n
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indices = list(range(n))
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cycles = list(range(n - r + 1, n + 1))[::-1]
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yield tuple(pool[i] for i in indices[:r])
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while n:
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for i in reversed(range(r)):
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cycles[i] -= 1
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if cycles[i] == 0:
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indices[i:] = indices[i + 1 :] + indices[i : i + 1]
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cycles[i] = n - i
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else:
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j = cycles[i]
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indices[i], indices[-j] = indices[-j], indices[i]
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yield tuple(pool[i] for i in indices[:r])
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break
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else:
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return
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# From http://code.activestate.com/recipes/576647/
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def n_queens(queen_count):
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"""N-Queens solver.
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Args: queen_count: the number of queens to solve for, same as board size.
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Yields: Solutions to the problem, each yielded value is a N-tuple.
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"""
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cols = range(queen_count)
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for vec in permutations(cols):
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if queen_count == len(set(vec[i] + i for i in cols)) == len(set(vec[i] - i for i in cols)):
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yield vec
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###########################################################################
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# Benchmark interface
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bm_params = {
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(50, 25): (1, 5),
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(100, 25): (1, 6),
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(1000, 100): (1, 7),
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(5000, 100): (1, 8),
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}
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def bm_setup(params):
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res = None
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def run():
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nonlocal res
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for _ in range(params[0]):
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res = len(list(n_queens(params[1])))
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def result():
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return params[0] * 10 ** (params[1] - 3), res
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return run, result
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