The working of perms

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Seetha Rama Raju Sanapala
编辑： Jan 2015-10-18
I tried perms('abc'). The doc says it is permutations in reverse lexicographic order. So I expected from the bottom - abc, acb, bac, bca so on. But the result I got was acb, abc, bac, bca ..... Can any one explain what is going on?

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回答（2 个）

Thorsten
Thorsten 2015-10-15
Have a look at
perms(1:3)
The result you get with perms('abc') is analogous to this. To have lexicographic order, use
sortrows(perms('abc'))
  2 个评论
Guillaume
Guillaume 2015-10-15
编辑：Guillaume 2015-10-15
But the OP is correct. The doc is wrong and the order returned by perms is not reverse lexicograph.
For what it's worth, I've reported it to mathworks.
... and it's now been acknowledged as a bug.
Seetha Rama Raju Sanapala
Seetha Rama Raju Sanapala 2015-10-18
@Guillaume. Thank you.

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Jan
Jan 2015-10-18
编辑：Jan 2015-10-18
With Matlab R2011b I get:
perms('abc')
cba
cab
bca
bac
abc
acb
As reversed alphabetical order, I'd expect the last two lines to be swapped.
An efficient method to create the permutations in a sorted order: FEX: VChooseKO. But here the order is not "alphabetically" accoring to the contents of the input, but to the order of the values. So for an alphabetical order you'd need:
Str = 'acb';
VChooseKO(sort(Str), length(Str))

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