org.jgrapht.experimental.permutation

Class CompoundPermutationIter

java.lang.Object

org.jgrapht.experimental.permutation.CompoundPermutationIter

All Implemented Interfaces:

Iterator, ArrayPermutationsIter

public class CompoundPermutationIter
extends Object
implements ArrayPermutationsIter, Iterator

For permutation like this:

1. 1,2 are the same eq.group (numbers)
2. a,b are og the same eq.group (letters)
3. '$' is of its own eq. group (signs) Let the order of the group be (arbitrary): signs,numbers,letters (note that for performance reasons, this arbitrary order is the worst! see Performance section below)

These are the possible compound perm: [$,1,2,a,b,c]

[$,1,2,a,c,b]

[$,1,2,b,a,c]

[$,1,2,b,c,a]

[$,1,2,c,a,b]

[$,1,2,c,b,a]

[$,2,1,a,b,c]

[$,2,1,a,c,b]

[$,2,1,b,a,c]

[$,2,1,b,c,a]

[$,2,1,c,a,b]

[$,2,1,c,b,a]

The overall number is the product of the factorials of each eq. group size; in our example : (1!)x(2!)x(3!)=1x2x6=12. Using the constructor with eq.group sizes and initial order [1,2,3], the result permutations are retrieved as numbers in an array, where [0,1,2,3,4,5] means [$,1,2,a,b,c]:

[0,1,2,3,5,4]

[0,1,2,4,3,5]

etc. etc., till:

[0,2,1,5,4,3] means [$,2,1,c,b,a]

Performance: The implementation tries to advance each time the group zero, if it does not succeed, it tries the next group (1,2 and so on), so: try to put the largest group as the first groups, UNLIKE the example. Performance-wise it is better to do [a,b,c,1,2,$] .The effect is improvement by constant (for example, by 2)

Since:

May 30, 2005

Author:

Assaf

Constructor Summary

Constructors

Constructor and Description
CompoundPermutationIter(int[] equalityGroupsSizesArray) For the class example, use [1,2,2].

Method Summary

Methods

Modifier and Type	Method and Description
int	getMax()
int[]	getNext() Iteration may be one of these two: 1.
int[]	getPermAsArray() Creates and returns a new array which consists of the eq.
boolean	hasNext()
boolean	hasNextPermutaions()
Object	next()
int[]	nextPermutation()
void	remove() UNIMPLEMENTED.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CompoundPermutationIter

public CompoundPermutationIter(int[] equalityGroupsSizesArray)

For the class example, use [1,2,2]. order matters! (performance-wise too)

Parameters:

equalityGroupsSizesArray -

Method Detail

next

public Object next()

Specified by:

next in interface Iterator

getNext

public int[] getNext()

Iteration may be one of these two: 1. the last group advances by one iter, all else stay. 2. the last group cannot advance , so it restarts but telling the group after it to advance (done recursively till some group can advance)

getPermAsArray

public int[] getPermAsArray()

Creates and returns a new array which consists of the eq. group current permutation arrays. For example, in the 10th iter ([$,2,1,b,c,a]) The permutations current statuses is [0] [2,1] [4,5,3] so retrieve [0,2,1,4,5,3]

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator

getMax

public int getMax()

nextPermutation

public int[] nextPermutation()

Specified by:

nextPermutation in interface ArrayPermutationsIter

hasNextPermutaions

public boolean hasNextPermutaions()

Specified by:

hasNextPermutaions in interface ArrayPermutationsIter

remove

public void remove()

UNIMPLEMENTED. always throws new UnsupportedOperationException

Specified by:

remove in interface Iterator

See Also:

Iterator.remove()