Permutations: Difference between revisions

=== Implementation using destructive list updates ===

<lang python>

def permutations(xs):

ac = [[]]

for x in xs:

ac_new = []

for ts in ac:

for n in range(0,ts.__len__()+1):

new_ts = ts[:] #(shallow) copy of ts

new_ts.insert(n,x)

ac_new.append(new_ts)

ac=ac_new

return ac

print(permutations([1,2,3,4]))

</lang>