NUPerms

Next Unique Permutation of an integer vector

Description

[PermOut, last] = NUPerms(PermIn) uses a simple and efficient iterative algorithm to return the permutation vector that follows PermIn in lexicographical order, discarding replicates.

This is much faster than finding all permutations with perms and then discarding replicates. Moreover, calling the function iteratively, one can explore all permutations of a given vector without having to store them in memory.

If PermIn is the last vector in lexicographical order, then PermOut=PermIn and last is set to 1, otherwise last is set to 0.

[P,last]=NUPerms([0 0 1])
  P = 0 1 0
  last = 0

[P,last]=NUPerms([1 0 0])
  P = 1 0 0
  last = 1

• MATLAB release: MATLAB 7.11 (R2010b)

[David Holdaway]

Can't say I'm convinced this is quicker than just generating all the permutations with perms and post selecting, calling very quick functions recursively in Matlab is not efficient at all really.
If you just want just ONE permutation it is obviously faster and not having to store them in memory is probably nice.

There is one thing I am however confused about, which is why you have made this work only for integers, there is nothing in the logic that would mean it shouldn't work fine for double precision numbers why not let the function use the same class as the input?