Permutations by swapping: Difference between revisions

=={{header|11l}}==

{{trans|Python: Iterative version of the recursive}}

<lang 11l>F s_permutations(seq)

V items = [[Int]()]

L(j) seq

[[Int]] new_items

L(item) items

V i = L.index

I i % 2

new_items [+]= (0..item.len).map(i -> @item[0 .< i] [+] [@j] [+] @item[i ..])

E

new_items [+]= (item.len..0).step(-1).map(i -> @item[0 .< i] [+] [@j] [+] @item[i ..])

items = new_items

R enumerate(items).map((i, item) -> (item, I i % 2 {-1} E 1))

L(n) (3, 4)

print(‘Permutations and sign of #. items’.format(n))

L(perm, sgn) s_permutations(Array(0 .< n))

print(‘Perm: #. Sign: #2’.format(perm, sgn))

print()</lang>

{{out}}

<pre>

Permutations and sign of 3 items

Perm: [0, 1, 2] Sign: 1

Perm: [0, 2, 1] Sign: -1

Perm: [2, 0, 1] Sign: 1

Perm: [2, 1, 0] Sign: -1

Perm: [1, 2, 0] Sign: 1

Perm: [1, 0, 2] Sign: -1

Permutations and sign of 4 items

Perm: [0, 1, 2, 3] Sign: 1

Perm: [0, 1, 3, 2] Sign: -1

Perm: [0, 3, 1, 2] Sign: 1

Perm: [3, 0, 1, 2] Sign: -1

Perm: [3, 0, 2, 1] Sign: 1

Perm: [0, 3, 2, 1] Sign: -1

Perm: [0, 2, 3, 1] Sign: 1

Perm: [0, 2, 1, 3] Sign: -1

Perm: [2, 0, 1, 3] Sign: 1

Perm: [2, 0, 3, 1] Sign: -1

Perm: [2, 3, 0, 1] Sign: 1

Perm: [3, 2, 0, 1] Sign: -1

Perm: [3, 2, 1, 0] Sign: 1

Perm: [2, 3, 1, 0] Sign: -1

Perm: [2, 1, 3, 0] Sign: 1

Perm: [2, 1, 0, 3] Sign: -1

Perm: [1, 2, 0, 3] Sign: 1

Perm: [1, 2, 3, 0] Sign: -1

Perm: [1, 3, 2, 0] Sign: 1

Perm: [3, 1, 2, 0] Sign: -1

Perm: [3, 1, 0, 2] Sign: 1

Perm: [1, 3, 0, 2] Sign: -1

Perm: [1, 0, 3, 2] Sign: 1

Perm: [1, 0, 2, 3] Sign: -1

</pre>