Class IndirectSort


  • public final class IndirectSort
    extends java.lang.Object
    Sorting routines that return an array of sorted indices implied by a given comparator rather than move elements of whatever the comparator is using for comparisons.

    A practical use case for this class is when the index of an array is meaningful and one wants to acquire the order of values in that array. None of the methods in Java Collections would provide such functionality directly and creating a collection of boxed Integer objects for indices seems to be too costly.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static int[] mergesort​(int start, int length, IndirectComparator comparator)
      Returns the order of elements between indices start and length, as indicated by the given comparator.
      static <T> int[] mergesort​(T[] input, int start, int length, java.util.Comparator<? super T> comparator)
      Returns the order of elements between indices start and length, as indicated by the given comparator.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Method Detail

      • mergesort

        public static int[] mergesort​(int start,
                                      int length,
                                      IndirectComparator comparator)
        Returns the order of elements between indices start and length, as indicated by the given comparator.

        This routine uses merge sort. It is guaranteed to be stable.

      • mergesort

        public static <T> int[] mergesort​(T[] input,
                                          int start,
                                          int length,
                                          java.util.Comparator<? super T> comparator)
        Returns the order of elements between indices start and length, as indicated by the given comparator. This method is equivalent to calling mergesort(int, int, IndirectComparator) with IndirectComparator.DelegatingComparator.

        This routine uses merge sort. It is guaranteed to be stable.