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September Morn Update

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Ingy döt Net 2019-09-12 10:33:56 -07:00
parent 4e2d22a71d
commit aac6731f2c
6856 changed files with 141342 additions and 21127 deletions
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22
Task/N-queens-problem/Python/n-queens-problem-6.py
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@ -1,4 +1,4 @@
def queens_lex(n):
def queens(n):
a = list(range(n))
up = [True]*(2*n - 1)
down = [True]*(2*n - 1)
@ -7,25 +7,17 @@ def queens_lex(n):
yield tuple(a)
else:
for k in range(i, n):
a[i], a[k] = a[k], a[i]
j = a[i]
j = a[k]
p = i + j
q = i - j + n - 1
if up[p] and down[q]:
up[p] = down[q] = False
a[i], a[k] = a[k], a[i]
yield from sub(i + 1)
up[p] = down[q] = True
x = a[i]
for k in range(i + 1, n):
a[k - 1] = a[k]
a[n - 1] = x
a[i], a[k] = a[k], a[i]
yield from sub(0)
next(queens(31))
(0, 2, 4, 1, 3, 8, 10, 12, 14, 6, 17, 21, 26, 28, 25, 27, 24, 30, 7, 5, 29, 15, 13, 11, 9, 18, 22, 19, 23, 16, 20)
next(queens_lex(31))
(0, 2, 4, 1, 3, 8, 10, 12, 14, 5, 17, 22, 25, 27, 30, 24, 26, 29, 6, 16, 28, 13, 9, 7, 19, 11, 15, 18, 21, 23, 20)
#Compare to A065188
#1, 3, 5, 2, 4, 9, 11, 13, 15, 6, 8, 19, 7, 22, 10, 25, 27, 29, 31, 12, 14, 35, 37, ...
#Count solutions for n=8:
sum(1 for p in queens(8))
92