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## Class template skew_heap

boost::heap::skew_heap — skew heap

## Synopsis

    // In header: <boost/heap/skew_heap.hpp>

    template<typename T, class... Options>
    class skew_heap {
    public:
      // types
      typedef T                                                                                   value_type;
      typedef implementation_defined::size_type                                                   size_type;
      typedef implementation_defined::difference_type                                             difference_type;
      typedef implementation_defined::value_compare                                               value_compare;
      typedef implementation_defined::allocator_type                                              allocator_type;
      typedef implementation_defined::reference                                                   reference;
      typedef implementation_defined::const_reference                                             const_reference;
      typedef implementation_defined::pointer                                                     pointer;
      typedef implementation_defined::const_pointer                                               const_pointer;
      typedef implementation_defined::iterator                                                    iterator;
      typedef implementation_defined::const_iterator                                              const_iterator;
      typedef implementation_defined::ordered_iterator                                            ordered_iterator;
      typedef mpl::if_c< is_mutable, typename implementation_defined::handle_type, void * >::type handle_type;

      // member classes/structs/unions

      struct implementation_defined {
        // types
        typedef T                               value_type;
        typedef base_maker::compare_argument    value_compare;
        typedef base_maker::allocator_type      allocator_type;
        typedef base_maker::node_type           node;
        typedef allocator_type::pointer         node_pointer;
        typedef allocator_type::const_pointer   const_node_pointer;
        typedef unspecified                     value_extractor;
        typedef boost::array< node_pointer, 2 > child_list_type;
        typedef child_list_type::iterator       child_list_iterator;
        typedef unspecified                     iterator;
        typedef iterator                        const_iterator;
        typedef unspecified                     ordered_iterator;
        typedef unspecified                     reference;
        typedef unspecified                     handle_type;
      };

      // construct/copy/destruct
      explicit skew_heap(value_compare const & = value_compare());
      skew_heap(skew_heap const &);
      skew_heap(skew_heap &&);
      skew_heap& operator=(skew_heap const &);
      skew_heap& operator=(skew_heap &&);
      ~skew_heap(void);

      // public member functions
      mpl::if_c< is_mutable, handle_type, void >::type push(value_type const &);
      template<typename... Args>
        mpl::if_c< is_mutable, handle_type, void >::type emplace(Args &&...);
      bool empty(void) const;
      size_type size(void) const;
      size_type max_size(void) const;
      void clear(void);
      allocator_type get_allocator(void) const;
      void swap(skew_heap &);
      const_reference top(void) const;
      void pop(void);
      iterator begin(void) const;
      iterator end(void) const;
      ordered_iterator ordered_begin(void) const;
      ordered_iterator ordered_end(void) const;
      void merge(skew_heap &);
      value_compare const & value_comp(void) const;
      template<typename HeapType> bool operator<(HeapType const &) const;
      template<typename HeapType> bool operator>(HeapType const &) const;
      template<typename HeapType> bool operator>=(HeapType const &) const;
      template<typename HeapType> bool operator<=(HeapType const &) const;
      template<typename HeapType> bool operator==(HeapType const &) const;
      template<typename HeapType> bool operator!=(HeapType const &) const;
      void erase(handle_type);
      void update(handle_type, const_reference);
      void update(handle_type);
      void increase(handle_type, const_reference);
      void increase(handle_type);
      void decrease(handle_type, const_reference);
      void decrease(handle_type);

      // public static functions
      static handle_type s_handle_from_iterator(iterator const &);

      // public data members
      static const bool constant_time_size;
      static const bool has_ordered_iterators;
      static const bool is_mergable;
      static const bool is_stable;
      static const bool has_reserve;
      static const bool is_mutable;
    };

## Description

The template parameter T is the type to be managed by the container. The user can specify additional options and if no options are provided default options are used.

The container supports the following options:

- `boost::heap::compare<>`, defaults to `compare<std::less<T>` >

- `boost::heap::stable<>`, defaults to `stable<false>`

- `boost::heap::stability_counter_type<>`, defaults to `stability_counter_type<boost::uintmax_t>`

- `boost::heap::allocator<>`, defaults to `allocator<std::allocator<T>` >

- `boost::heap::constant_time_size<>`, defaults to `constant_time_size<true>`

- `boost::heap::store_parent_pointer<>`, defaults to `store_parent_pointer<true>`. Maintaining a parent pointer adds some maintenance and size overhead, but iterating a heap is more efficient.

- `boost::heap::mutable<>`, defaults to `mutable<false>`.

### `skew_heap` public types

1. typedef implementation_defined::iterator iterator;

   Note: The iterator does not traverse the priority queue in order of the priorities.

### `skew_heap` public construct/copy/destruct

1.     explicit skew_heap(value_compare const & cmp = value_compare());

   Effects: constructs an empty priority queue.

   Complexity: Constant.

2.     skew_heap(skew_heap const & rhs);

   Effects: copy-constructs priority queue from rhs.

   Complexity: Linear.

3.     skew_heap(skew_heap && rhs);

   Effects: C++11-style move constructor.

   Complexity: Constant.

   Note: Only available, if BOOST_HAS_RVALUE_REFS is defined

4.     skew_heap& operator=(skew_heap const & rhs);

   Effects: Assigns priority queue from rhs.

   Complexity: Linear.

5.     skew_heap& operator=(skew_heap && rhs);

   Effects: C++11-style move assignment.

   Complexity: Constant.

   Note: Only available, if BOOST_HAS_RVALUE_REFS is defined

6.     ~skew_heap(void);

### `skew_heap` public member functions

1.     mpl::if_c< is_mutable, handle_type, void >::type push(value_type const & v);

   Effects: Adds a new element to the priority queue.

   Complexity: Logarithmic (amortized).

2.     template<typename... Args>
         mpl::if_c< is_mutable, handle_type, void >::type emplace(Args &&... args);

   Effects: Adds a new element to the priority queue. The element is directly constructed in-place.

   Complexity: Logarithmic (amortized).

3.     bool empty(void) const;

   Effects: Returns true, if the priority queue contains no elements.

   Complexity: Constant.

4.     size_type size(void) const;

   Effects: Returns the number of elements contained in the priority queue.

   Complexity: Constant, if configured with constant_time_size<true>, otherwise linear.

5.     size_type max_size(void) const;

   Effects: Returns the maximum number of elements the priority queue can contain.

   Complexity: Constant.

6.     void clear(void);

   Effects: Removes all elements from the priority queue.

   Complexity: Linear.

7.     allocator_type get_allocator(void) const;

   Effects: Returns allocator.

   Complexity: Constant.

8.     void swap(skew_heap & rhs);

   Effects: Swaps two priority queues.

   Complexity: Constant.

9.     const_reference top(void) const;

   Effects: Returns a const_reference to the maximum element.

   Complexity: Constant.

10.     void pop(void);

    Effects: Removes the top element from the priority queue.

    Complexity: Logarithmic (amortized).

11.     iterator begin(void) const;

    Effects: Returns an iterator to the first element contained in the priority queue.

    Complexity: Constant.

12.     iterator end(void) const;

    Effects: Returns an iterator to the end of the priority queue.

    Complexity: Constant.

13.     ordered_iterator ordered_begin(void) const;

    Effects: Returns an ordered iterator to the first element contained in the priority queue.

    Note: Ordered iterators traverse the priority queue in heap order.

14.     ordered_iterator ordered_end(void) const;

    Effects: Returns an ordered iterator to the first element contained in the priority queue.

    Note: Ordered iterators traverse the priority queue in heap order.

15.     void merge(skew_heap & rhs);

    Effects: Merge all elements from rhs into this

    Complexity: Logarithmic (amortized).

16.     value_compare const & value_comp(void) const;

    Effect: Returns the value_compare object used by the priority queue

17.     template<typename HeapType> bool operator<(HeapType const & rhs) const;

    Returns: Element-wise comparison of heap data structures

    Requirement: the `value_compare` object of both heaps must match.

18.     template<typename HeapType> bool operator>(HeapType const & rhs) const;

    Returns: Element-wise comparison of heap data structures

    Requirement: the `value_compare` object of both heaps must match.

19.     template<typename HeapType> bool operator>=(HeapType const & rhs) const;

    Returns: Element-wise comparison of heap data structures

    Requirement: the `value_compare` object of both heaps must match.

20.     template<typename HeapType> bool operator<=(HeapType const & rhs) const;

    Returns: Element-wise comparison of heap data structures

    Requirement: the `value_compare` object of both heaps must match.

21.     template<typename HeapType> bool operator==(HeapType const & rhs) const;

    Equivalent comparison Returns: True, if both heap data structures are equivalent.

    Requirement: the `value_compare` object of both heaps must match.

22.     template<typename HeapType> bool operator!=(HeapType const & rhs) const;

    Equivalent comparison Returns: True, if both heap data structures are not equivalent.

    Requirement: the `value_compare` object of both heaps must match.

23.     void erase(handle_type object);

    Effects: Removes the element handled by `handle` from the `priority_queue`.

    Complexity: Logarithmic (amortized).

24.     void update(handle_type handle, const_reference v);

    Effects: Assigns `v` to the element handled by `handle` & updates the priority queue.

    Complexity: Logarithmic (amortized).

25.     void update(handle_type handle);

    Effects: Updates the heap after the element handled by `handle` has been changed.

    Complexity: Logarithmic (amortized).

    Note: If this is not called, after a handle has been updated, the behavior of the data structure is undefined!

26.     void increase(handle_type handle, const_reference v);

    Effects: Assigns `v` to the element handled by `handle` & updates the priority queue.

    Complexity: Logarithmic (amortized).

    Note: The new value is expected to be greater than the current one

27.     void increase(handle_type handle);

    Effects: Updates the heap after the element handled by `handle` has been changed.

    Complexity: Logarithmic (amortized).

    Note: If this is not called, after a handle has been updated, the behavior of the data structure is undefined!

28.     void decrease(handle_type handle, const_reference v);

    Effects: Assigns `v` to the element handled by `handle` & updates the priority queue.

    Complexity: Logarithmic (amortized).

    Note: The new value is expected to be less than the current one

29.     void decrease(handle_type handle);

    Effects: Updates the heap after the element handled by `handle` has been changed.

    Complexity: Logarithmic (amortized).

    Note: The new value is expected to be less than the current one. If this is not called, after a handle has been updated, the behavior of the data structure is undefined!

### `skew_heap` public static functions

1.     static handle_type s_handle_from_iterator(iterator const & it);

   Effects: Casts an iterator to a node handle.

   Complexity: Constant.

   Requirement: data structure must be configured as mutable