org.cicirello.permutations

Class PermutationIterator

java.lang.Object

org.cicirello.permutations.PermutationIterator

All Implemented Interfaces:

Iterator<Permutation>

public class PermutationIterator
extends Object
implements Iterator<Permutation>

Iterator over all permutations of a specified length, n, of the integers in the interval [0,n). The runtime of the constructors is O(n), where n is the permutation length. The hasNext() method is O(1). The runtime of the next() method is O(n), as it does O(n) swaps in the worst-case, and regardless of number of swaps it returns a copy (an O(n) operation) of the internally maintained Permutation object so the caller can safely modify the returned Permutation without risk of interfering with the operation of the Iterator.

Since:

1.2

Constructor Summary

Constructors

Constructor and Description
PermutationIterator(int n) Initializes a PermutationIterator to iterate over all permutations of a given length.
PermutationIterator(Permutation p) Initializes a PermutationIterator to iterate over all permutations the same length as a given permutation.

Method Summary

Modifier and Type	Method and Description
boolean	hasNext()
Permutation	next()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Iterator

forEachRemaining, remove

Constructor Detail

PermutationIterator

public PermutationIterator(int n)

Initializes a PermutationIterator to iterate over all permutations of a given length. Specifically, it iterates over permutations of the first n integers, i.e., the integers in the interval [0, n-1]. The first permutation in the iteration is chosen randomly.

Parameters:

n - The length of the permutations.

PermutationIterator

public PermutationIterator(Permutation p)

Initializes a PermutationIterator to iterate over all permutations the same length as a given permutation. Specifically, it iterates over permutations of the first n integers, i.e., the integers in the interval [0, n-1). The first permutation in the iteration is specified as a parameter.

Parameters:

p - The first permutation in the iteration.

Method Detail

hasNext

public boolean hasNext()

Specified by:

hasNext in interface Iterator<Permutation>

next

public Permutation next()

Specified by:

next in interface Iterator<Permutation>