Package org.apache.commons.numbers.arrays

Class KeyUpdatingInterval

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private int[] keys
      The ordered keys.
      private int l
      Index of the left key.
      private int r
      Index of the right key.
      private static int SCAN_SIZE
      Size to use a scan of the keys when splitting instead of binary search.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      (package private) KeyUpdatingInterval​(int[] indices, int n)
      Create an instance with the provided indices.
      private KeyUpdatingInterval​(int[] indices, int l, int r)  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int left()
      The start (inclusive) of the interval.
      int right()
      The end (inclusive) of the interval.
      (package private) static int searchLessOrEqual​(int[] a, int left, int right, int k)
      Search the data for the largest index i where a[i] is less-than-or-equal to the key; else return left - 1.
      (package private) int size()
      Return the current number of indices in the interval.
      UpdatingInterval splitLeft​(int ka, int kb)
      Split the interval using two splitting indices.
      int updateLeft​(int k)
      Update the left bound of the interval so k <= left.
      int updateRight​(int k)
      Update the right bound of the interval so right <= k.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • SCAN_SIZE

        private static final int SCAN_SIZE
        Size to use a scan of the keys when splitting instead of binary search. Note binary search has an overhead on small size due to the random left/right branching per iteration. It is much faster on very large sizes.
        See Also:
        Constant Field Values

      • keys

        private final int[] keys
        The ordered keys.

      • l

        private int l
        Index of the left key.

      • r

        private int r
        Index of the right key.

    • Constructor Detail

      • KeyUpdatingInterval

        KeyUpdatingInterval​(int[] indices,
                    int n)
        Create an instance with the provided indices.

        Warning: Indices must be sorted and distinct.

        Parameters:
        indices - Indices.
        n - Number of indices.

      • KeyUpdatingInterval

        private KeyUpdatingInterval​(int[] indices,
                            int l,
                            int r)
        Parameters:
        indices - Indices.
        l - Index of left key.
        r - Index of right key.

    • Method Detail

      • left

        public int left()
        Description copied from interface: UpdatingInterval
        The start (inclusive) of the interval.
        Specified by:
        left in interface UpdatingInterval
        Returns:
        start of the interval

      • right

        public int right()
        Description copied from interface: UpdatingInterval
        The end (inclusive) of the interval.
        Specified by:
        right in interface UpdatingInterval
        Returns:
        end of the interval

      • updateLeft

        public int updateLeft​(int k)
        Description copied from interface: UpdatingInterval
        Update the left bound of the interval so k <= left.

        Note: Requires left < k <= right, i.e. there exists a valid interval above the index. 

        
 l-----------k----------r
             |--> l
        Specified by:
        updateLeft in interface UpdatingInterval
        Parameters:
        k - Index to start checking from (inclusive).
        Returns:
        the new left

      • updateRight

        public int updateRight​(int k)
        Description copied from interface: UpdatingInterval
        Update the right bound of the interval so right <= k.

        Note: Requires left <= k < right, i.e. there exists a valid interval below the index. 

        
 l-----------k----------r
        r <--|
        Specified by:
        updateRight in interface UpdatingInterval
        Parameters:
        k - Index to start checking from (inclusive).
        Returns:
        the new right

      • splitLeft

        public UpdatingInterval splitLeft​(int ka,
                                  int kb)
        Description copied from interface: UpdatingInterval
        Split the interval using two splitting indices. Returns the left interval that occurs before the specified split index ka, and updates the current interval left bound to after the specified split index kb.

        Note: Requires left < ka <= kb < right, i.e. there exists a valid interval both above and below the splitting indices. 

        
 l-----------ka-kb----------r
      r1 <--|     |--> l1

 r1 < ka
 l1 > kb

        If ka <= left or kb >= right the result is undefined.

        Specified by:
        splitLeft in interface UpdatingInterval
        Parameters:
        ka - Split index.
        kb - Split index.
        Returns:
        the left interval

      • size

        int size()
        Return the current number of indices in the interval.
        Returns:
        the size

      • searchLessOrEqual

        static int searchLessOrEqual​(int[] a,
                             int left,
                             int right,
                             int k)
        Search the data for the largest index i where a[i] is less-than-or-equal to the key; else return left - 1. 
         a[i] <= k    :   left <= i <= right, or (left - 1)

        The data is assumed to be in ascending order, otherwise the behaviour is undefined. If the range contains multiple elements with the key value, the result index may be any that match.

        This is similar to using Arrays.binarySearch. The method differs in:

        • use of an inclusive upper bound;
        • returning the closest index with a value below key if no match was not found;
        • performing no range checks: it is assumed left <= right and they are valid indices into the array.

        An equivalent use of binary search is: 

        
 int i = Arrays.binarySearch(a, left, right + 1, k);
 if (i < 0) {
     i = ~i - 1;
 }

        This specialisation avoids the caller checking the binary search result for the use case when the presence or absence of a key is not important; only that the returned index for an absence of a key is the largest index. When used on unique keys this method can be used to update an upper index so all keys are known to be below a key: 

        
 int[] keys = ...
 // [i0, i1] contains all keys
 int i0 = 0;
 int i1 = keys.length - 1;
 // Update: [i0, i1] contains all keys <= k
 i1 = searchLessOrEqual(keys, i0, i1, k);
        Parameters:
        a - Data.
        left - Lower bound (inclusive).
        right - Upper bound (inclusive).
        k - Key.
        Returns:
        largest index i such that a[i] <= k, or left - 1 if no such index exists