Permutations by swapping: Difference between revisions
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Meanwhile, here's an inductive approach, using negative integers to look left and positive integers to look right:
<lang J>
lookingat=: 0 >. <:@# <. i.@# + *
next=: | >./@:* | > | {~ lookingat
Here,
To convert from the Steinhaus–Johnson–Trotter representation of a permutation to J's representation, use <:@|, or to find J's permutation index of a Steinhaus–Johnson–Trotter representation of a permutation, use A.<:@|
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Example use:
<lang J>
_1 _2 _3
_1 _3 _2
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_2 3 _1
_2 _1 3
<:@|
0 1 2
0 2 1
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1 2 0
1 0 2
A. <:@|
0 1 4 5 3 2</lang>
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