Package com.carrotsearch.hppc.sorting
Class IndirectSort
- java.lang.Object
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- com.carrotsearch.hppc.sorting.IndirectSort
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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.
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Field Summary
Fields Modifier and Type Field Description (package private) static int
MIN_LENGTH_FOR_INSERTION_SORT
Minimum window length to apply insertion sort in merge sort.
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Constructor Summary
Constructors Modifier Constructor Description private
IndirectSort()
No instantiation.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description private static int[]
createOrderArray(int start, int length)
Creates the initial order array.private static void
insertionSort(int off, int len, int[] order, IndirectComparator intComparator)
Internal insertion sort forint
s.static int[]
mergesort(int start, int length, IndirectComparator comparator)
Returns the order of elements between indicesstart
andlength
, as indicated by the givencomparator
.static <T> int[]
mergesort(T[] input, int start, int length, java.util.Comparator<? super T> comparator)
Returns the order of elements between indicesstart
andlength
, as indicated by the givencomparator
.private static void
topDownMergeSort(int[] src, int[] dst, int fromIndex, int toIndex, IndirectComparator comp)
Perform a recursive, descending merge sort.
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Method Detail
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mergesort
public static int[] mergesort(int start, int length, IndirectComparator comparator)
Returns the order of elements between indicesstart
andlength
, as indicated by the givencomparator
.This routine uses merge sort. It is guaranteed to be stable.
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mergesort
public static <T> int[] mergesort(T[] input, int start, int length, java.util.Comparator<? super T> comparator)
Returns the order of elements between indicesstart
andlength
, as indicated by the givencomparator
. This method is equivalent to callingmergesort(int, int, IndirectComparator)
withIndirectComparator.DelegatingComparator
.This routine uses merge sort. It is guaranteed to be stable.
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topDownMergeSort
private static void topDownMergeSort(int[] src, int[] dst, int fromIndex, int toIndex, IndirectComparator comp)
Perform a recursive, descending merge sort.- Parameters:
fromIndex
- inclusivetoIndex
- exclusive
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insertionSort
private static void insertionSort(int off, int len, int[] order, IndirectComparator intComparator)
Internal insertion sort forint
s.
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createOrderArray
private static int[] createOrderArray(int start, int length)
Creates the initial order array.
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