permutation ( n seq -- seq' )

Vocabulary

math.combinatorics

Inputs

n	a non-negative integer
seq	a sequence

Outputs

seq'	a sequence

Word description

Outputs the nth lexicographical permutation of seq.

Notes

Permutations are 0-based and a bounds error will be thrown if n is larger than seq length factorial 1 -.

Examples

USING: math.combinatorics prettyprint ; 1 { 0 1 2 } permutation .
{ 0 2 1 }

USING: math.combinatorics prettyprint ; 5 { "apple" "banana" "orange" } permutation .
{ "orange" "banana" "apple" }

Definition

USING: kernel math.combinatorics.private ;

IN: math.combinatorics

: permutation ( n seq -- seq' )
    [ permutation-indices ] keep nths-unsafe ;