Package org.neo4j.gds.core.utils

Class ArrayLayout

  • public final class ArrayLayout
extends java.lang.Object

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static long[] constructEytzinger​(long[] input)
      Constructs a new binary search tree using the Eytzinger layout.
      static ArrayLayout.LayoutAndSecondary constructEytzinger​(long[] input, int[] secondary)
      Constructs a new binary search tree using the Eytzinger layout.
      static long[] constructEytzinger​(long[] input, int offset, int length)
      Constructs a new binary search tree using the Eytzinger layout.
      static int searchEytzinger​(long[] haystack, long needle)
      Searches for the needle in the haystack, returning an index pointing at the needle.

      • Methods inherited from class java.lang.Object

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

    • Method Detail

      • constructEytzinger

        public static long[] constructEytzinger​(long[] input)
        Constructs a new binary search tree using the Eytzinger layout. Input must be sorted.
        Parameters:
        input - the sorted input data

      • constructEytzinger

        public static long[] constructEytzinger​(long[] input,
                                        int offset,
                                        int length)
        Constructs a new binary search tree using the Eytzinger layout. Input must be sorted.
        Parameters:
        input - the sorted input data
        offset - where to start at in the input
        length - how many elements to use from the input

      • constructEytzinger

        public static ArrayLayout.LayoutAndSecondary constructEytzinger​(long[] input,
                                                                int[] secondary)
        Constructs a new binary search tree using the Eytzinger layout. Input must be sorted. A secondary array is permuted in the same fashion as the input array.
        Parameters:
        input - the sorted input data
        secondary - secondary values that are permuted as well

      • searchEytzinger

        public static int searchEytzinger​(long[] haystack,
                                  long needle)
        Searches for the needle in the haystack, returning an index pointing at the needle. The array must be one constructed from constructEytzinger(long[]) or related. Any other order of the array (e.g. sorted for binary search) will produce undefined results. Unlike Arrays.binarySearch(long[], long), this method returns the index of the value that is either equal to the needle or the next smallest one. There are no different results to signal whether a value was found or not. If you need to know whether the value is contained in the array, you need to compare the value against the array at the position of the returned index. The index returned is the last index where the value is not larger than the needle. This is also different from the j.u.Arrays method. That one returns "the index of the first element greater than the key", that is the upper bound of the search. Starting from that index upto the end of the array, all values are either equal to or greater than the needle. In contrast, this method returns the lower bound. Starting from 0 up to, and including, the returned index, all values are either less than or equal to the needle.
        Parameters:
        haystack - the input array sorted and constructed by constructEytzinger(long[])
        needle - the needle to search for
        Returns:
        the lower bound for the needle. Either the index of the needle if it was in the array or the index preceding the place where the needle would be. Note that, unlike the sibling method Arrays.binarySearch(long[], long), the index returned *cannot* be used to change the contents of the search array.