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zopieux/kth_perm.py

Created July 24, 2017 14:32
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kth permutation
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kth_perm.py
def kth_perm(n, k):
res = list(range(n))
for i in range(n):
f = math.factorial(n - i - 1)
s, m = divmod(k, f)
if m == 0 and s == 0:
break
if s > 0:
for j in range(i - 1 + s, i - 1, -1):
res[j-1], res[j] = res[j], res[j-1]
if m == 0:
break
k = m
return res
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