Module org.cicirello.jpt
Package org.cicirello.permutations

Class 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.

    • 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()
        Checks if this PermutationIterator has more Permutations.
        Specified by:
        hasNext in interface Iterator<Permutation>
        Returns:
        true if and only if this PermutationIterator has more Permutations to iterate over.