cc.redberry.combinatorics

Class IntPermutations

java.lang.Object

cc.redberry.combinatorics.IntPermutations

All Implemented Interfaces:

CombinatorialIterator<int[]>, Serializable, Iterable<int[]>, Iterator<int[]>

public final class IntPermutations
extends Object
implements CombinatorialIterator<int[]>

Iterator over all possible permutations.

Example

 IntPermutations its = new IntPermutations(3);
 while (its.hasNext())
     System.out.println(Arrays.toString(its.next()))
 

The result will be

      [0, 1, 2]
      [0, 2, 1]
      [1, 0, 2]
      [1, 2, 0]
      [2, 0, 1]
      [2, 1, 0]
 

It is also possible to iterate in the opposite direction via previous() method.

The iterator is implemented such that each next combination will be calculated only on the invocation of method next().

Note: method next() returns the same reference on each invocation.

Since:

1.0

Author:

Dmitry Bolotin, Stanislav Poslavsky

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
IntPermutations(int dimension) Construct iterator over all permutations with specified dimension starting with identity.
IntPermutations(int[] permutation) Construct iterator over permutations with specified permutation at the start.

Method Summary

Modifier and Type	Method and Description
int[]	current() Returns the reference on the current iteration element.
int	getDimension() Returns dimension specified in the constructor
boolean	hasNext()
boolean	hasPrevious() Returns true if the iteration has more elements, iterating in back order.
int[]	next() Returns the next element in the iteration.
int[]	previous() Returns the previous element in the iteration.
void	remove()
void	reset() Resets the iteration

Methods inherited from class java.lang.Object

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

Methods inherited from interface cc.redberry.combinatorics.CombinatorialIterator

iterator, stream, toList

Methods inherited from interface java.util.Iterator

forEachRemaining

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Detail

IntPermutations

public IntPermutations(int dimension)

Construct iterator over all permutations with specified dimension starting with identity.

Parameters:

dimension - dimension of permutations

IntPermutations

public IntPermutations(int[] permutation)

Construct iterator over permutations with specified permutation at the start. If starting permutation is not identity, the iterator will not iterate over all possible permutations, but only from starting permutation up to the last permutation, which is [size-1,size-2,....1,0].

Note: parameter permutation is not copied in constructor and the same instance will be used during iteration.

Parameters:

permutation - starting permutation

Throws:

IllegalArgumentException - if permutation is inconsistent with one-line notation

Method Detail

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<int[]>

hasPrevious

public boolean hasPrevious()

Returns true if the iteration has more elements, iterating in back order. (In other words, returns true if previous() would return an element rather than throwing an exception.)

Returns:

true if the iteration has more elements

next

public int[] next()

Returns the next element in the iteration.

Specified by:

next in interface Iterator<int[]>

Returns:

the next element in the iteration

previous

public int[] previous()

Returns the previous element in the iteration.

Returns:

the previous element in the iteration

reset

public void reset()

Description copied from interface: CombinatorialIterator

Resets the iteration

Specified by:

reset in interface CombinatorialIterator<int[]>

remove

public void remove()

Specified by:

remove in interface Iterator<int[]>

Throws:

UnsupportedOperationException - always

getDimension

public int getDimension()

Returns dimension specified in the constructor

Returns:

dimension specified in the constructor

current

public int[] current()

Description copied from interface: CombinatorialIterator

Returns the reference on the current iteration element.

Specified by:

current in interface CombinatorialIterator<int[]>

Returns:

the reference on the current iteration element