Class IntroSelector

  • public abstract class IntroSelector
    extends Selector
    Adaptive selection algorithm based on the introspective quick select algorithm. The quick select algorithm uses an interpolation variant of Tukey's ninther median-of-medians for pivot, and Bentley-McIlroy 3-way partitioning. For the introspective protection, it shuffles the sub-range if the max recursive depth is exceeded.

    This selection algorithm is fast on most data shapes, especially on nearly sorted data, or when k is close to the boundaries. It runs in linear time on average.

    NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.
    • Constructor Detail

      • IntroSelector

        public IntroSelector()
    • Method Detail

      • select

        public final void select​(int from,
                                 int to,
                                 int k)
        Description copied from class: Selector
        Reorder elements so that the element at position k is the same as if all elements were sorted and all other elements are partitioned around it: [from, k) only contains elements that are less than or equal to k and (k, to) only contains elements that are greater than or equal to k.
        Specified by:
        select in class Selector
      • setPivot

        protected abstract void setPivot​(int i)
        Save the value at slot i so that it can later be used as a pivot, see comparePivot(int).
      • comparePivot

        protected abstract int comparePivot​(int j)
        Compare the pivot with the slot at j, similarly to compare(i, j).
      • compare

        protected int compare​(int i,
                              int j)
        Compare entries found in slots i and j. The contract for the returned value is the same as, Object).