I have N positions, and each position can be either 0 or 1. I have fixed number of 1s, and I want to permutate these fixed number of 1s in these N positions.
from itertools import permutations
p = [0 for k in xrange(6)]
for k in xrange(0,3):
p[k] = 1
print(list(permutations(p)))
But above result contains four [0,0,0,1,1,1] in the list. I only want one of them. How can I get rid of these duplicates?
You could grab the positions of the 1s instead:
from itertools import combinations
def place_ones(size, count):
for positions in combinations(range(size), count):
p = [0] * size
for i in positions:
p[i] = 1
yield p
In action:
>>> list(place_ones(6, 3))
[
[1, 1, 1, 0, 0, 0],
[1, 1, 0, 1, 0, 0],
[1, 1, 0, 0, 1, 0],
[1, 1, 0, 0, 0, 1],
[1, 0, 1, 1, 0, 0],
[1, 0, 1, 0, 1, 0],
[1, 0, 1, 0, 0, 1],
[1, 0, 0, 1, 1, 0],
[1, 0, 0, 1, 0, 1],
[1, 0, 0, 0, 1, 1],
[0, 1, 1, 1, 0, 0],
[0, 1, 1, 0, 1, 0],
[0, 1, 1, 0, 0, 1],
[0, 1, 0, 1, 1, 0],
[0, 1, 0, 1, 0, 1],
[0, 1, 0, 0, 1, 1],
[0, 0, 1, 1, 1, 0],
[0, 0, 1, 1, 0, 1],
[0, 0, 1, 0, 1, 1],
[0, 0, 0, 1, 1, 1],
]
Set is perfect for this, as set does not not contain any duplicated element:
set(permutations(p))
sorted([e for e in set(permutations(p))]) convert set into list, optionaly sort to impose an ordering
what you are looking for is a multiset permutation.
sympy provides the function multiset_permutations:
from sympy.utilities.iterables import multiset_permutations
n_zeros, n_ones = 3, 3
for perm in multiset_permutations(n_zeros * (0,) + n_ones * (1,)):
print(perm)
which outputs:
[0, 0, 0, 1, 1, 1]
[0, 0, 1, 0, 1, 1]
[0, 0, 1, 1, 0, 1]
[0, 0, 1, 1, 1, 0]
[0, 1, 0, 0, 1, 1]
[0, 1, 0, 1, 0, 1]
[0, 1, 0, 1, 1, 0]
[0, 1, 1, 0, 0, 1]
[0, 1, 1, 0, 1, 0]
[0, 1, 1, 1, 0, 0]
[1, 0, 0, 0, 1, 1]
[1, 0, 0, 1, 0, 1]
[1, 0, 0, 1, 1, 0]
[1, 0, 1, 0, 0, 1]
[1, 0, 1, 0, 1, 0]
[1, 0, 1, 1, 0, 0]
[1, 1, 0, 0, 0, 1]
[1, 1, 0, 0, 1, 0]
[1, 1, 0, 1, 0, 0]
[1, 1, 1, 0, 0, 0]
