Package org.jheaps.tree

Class LeftistHeap<K,​V>

  • Type Parameters:
    K - the type of keys maintained by this heap
    V - the type of values maintained by this heap
    All Implemented Interfaces:
    java.io.Serializable, AddressableHeap<K,​V>, MergeableAddressableHeap<K,​V>
    public class LeftistHeap<K,​V>
extends SkewHeap<K,​V>
    Leftist heaps. The heap is sorted according to the natural ordering of its keys, or by a Comparator provided at heap creation time, depending on which constructor is used.

    Operations insert, deleteMin, decreaseKey, and delete take worst-case O(log(n)). Operation findMin is worst-case O(1).

    Note that the ordering maintained by this heap, like any heap, and whether or not an explicit comparator is provided, must be consistent with equals if this heap is to correctly implement the Heap interface. (See Comparable or Comparator for a precise definition of consistent with equals.) This is so because the Heap interface is defined in terms of the equals operation, but this heap performs all key comparisons using its compareTo (or compare) method, so two keys that are deemed equal by this method are, from the standpoint of this heap, equal. The behavior of a heap is well-defined even if its ordering is inconsistent with equals; it just fails to obey the general contract of the Heap interface.

    Note that this implementation is not synchronized. If multiple threads access a heap concurrently, and at least one of the threads modifies the heap structurally, it must be synchronized externally. (A structural modification is any operation that adds or deletes one or more elements or changing the key of some element.) This is typically accomplished by synchronizing on some object that naturally encapsulates the heap.

    See Also:
    Serialized Form

    • Constructor Detail

      • LeftistHeap

        public LeftistHeap()
        Constructs a new, empty heap, using the natural ordering of its keys.

        All keys inserted into the heap must implement the Comparable interface. Furthermore, all such keys must be mutually comparable: k1.compareTo(k2) must not throw a ClassCastException for any keys k1 and k2 in the heap. If the user attempts to put a key into the heap that violates this constraint (for example, the user attempts to put a string key into a heap whose keys are integers), the insert(Object key) call will throw a ClassCastException.

      • LeftistHeap

        public LeftistHeap​(java.util.Comparator<? super K> comparator)
        Constructs a new, empty heap, ordered according to the given comparator.

        All keys inserted into the heap must be mutually comparable by the given comparator: comparator.compare(k1, k2) must not throw a ClassCastException for any keys k1 and k2 in the heap. If the user attempts to put a key into the heap that violates this constraint, the insert(Object key) call will throw a ClassCastException.

        Parameters:
        comparator - the comparator that will be used to order this heap. If null, the natural ordering of the keys will be used.

    • Method Detail

      • createNode

        protected SkewHeap.Node<K,​V> createNode​(K key,
                                              V value)
        Factory method for new node creation
        Overrides:
        createNode in class SkewHeap<K,​V>
        Parameters:
        key - the key
        value - the value
        Returns:
        the newly created node

      • swapChildren

        protected void swapChildren​(SkewHeap.Node<K,​V> n)
        Swap the children of a node.
        Parameters:
        n - the node

      • union

        protected SkewHeap.Node<K,​V> union​(SkewHeap.Node<K,​V> root1,
                                         SkewHeap.Node<K,​V> root2)
        Top-down union two skew heaps
        Overrides:
        union in class SkewHeap<K,​V>
        Parameters:
        root1 - the root of the first heap
        root2 - the root of the right heap
        Returns:
        the new root of the merged heap

      • unionWithComparator

        protected SkewHeap.Node<K,​V> unionWithComparator​(SkewHeap.Node<K,​V> root1,
                                                       SkewHeap.Node<K,​V> root2)
        Top-down union of two leftist heaps with comparator.
        Overrides:
        unionWithComparator in class SkewHeap<K,​V>
        Parameters:
        root1 - the root of the first heap
        root2 - the root of the right heap
        Returns:
        the new root of the merged heap