Package groovy.util

Class PermutationGenerator<E>

  • All Implemented Interfaces:

    public class PermutationGenerator<E>
    extends Object
    implements Iterator<List<E>>
    Systematically generate permutations. Adapted from Java Code by Michael Gilleland (released with no restrictions) using an algorithm described here: Kenneth H. Rosen, Discrete Mathematics and Its Applications, 2nd edition (NY: McGraw-Hill, 1991), pp. 282-284
    • Constructor Detail

      • PermutationGenerator

        public PermutationGenerator​(Collection<E> items)
        WARNING: Don't make n too large. Recall that the number of permutations is n! which can be very large, even when n is as small as 20 -- 20! = 2,432,902,008,176,640,000 and 21! is too big to fit into a Java long, which is why we use BigInteger instead.
        items - the items to permute
      • PermutationGenerator

        public PermutationGenerator​(Iterable<E> items)
    • Method Detail

      • reset

        public void reset()
      • hasNext

        public boolean hasNext()
        Specified by:
        hasNext in interface Iterator<E>
      • next

        public List<E> next()
        Generate next permutation (algorithm from Rosen p. 284)
        Specified by:
        next in interface Iterator<E>
        the items permuted
      • remove

        public void remove()
        Specified by:
        remove in interface Iterator<E>