/ CLASS PROVIDED: p_queue (priority queue ADT) // TYPEDEFS and MEMBER CONSTANTS for the p_queue class: //   typedef _____ value_type //     p_queue::value_type is the data type of the items in //     the p_queue. It may be any of the C++ built-in types //     (int, char, etc.), or a class with a default constructor, a //     copy constructor, an assignment operator, and a less-than operator forming a strict weak ordering. //   typedef _____ size_type //     p_queue::size_type is the data type considered best-suited //     for any variable meant for counting and sizing (as well as //     array-indexing) purposes; e.g.: it is the data type for a //     variable representing how many items are in the p_queue. //     It is also the data type of the priority associated with //     each item in the p_queue

// CLASS PROVIDED: p_queue (priority queue ADT)
// TYPEDEFS and MEMBER CONSTANTS for the p_queue class:
//   typedef _____ value_type
//     p_queue::value_type is the data type of the items in
//     the p_queue. It may be any of the C++ built-in types
//     (int, char, etc.), or a class with a default constructor, a
//     copy constructor, an assignment operator, and a less-than operator forming a strict weak ordering.
//   typedef _____ size_type
//     p_queue::size_type is the data type considered best-suited
//     for any variable meant for counting and sizing (as well as
//     array-indexing) purposes; e.g.: it is the data type for a
//     variable representing how many items are in the p_queue.
//     It is also the data type of the priority associated with
//     each item in the p_queue
//   static const size_type DEFAULT_CAPACITY = _____
//    p_queue::DEFAULT_CAPACITY is the default initial capacity of a
//    p_queue that is created by the default constructor.
// CONSTRUCTOR for the p_queue class:
//   p_queue(size_type initial_capacity = DEFAULT_CAPACITY)
//     Pre:  initial_capacity > 0
//     Post: The p_queue has been initialized to an empty p_queue.
//       The push function will work efficiently (without allocating
//       new memory) until this capacity is reached.
//     Note: If Pre is not met, initial_capacity will be adjusted to
//       DEFAULT_CAPACITY. I.e., when creating a p_queue object,
//       client can override initial_capacity with something deemed
//       more appropriate than DEFAULT_CAPACITY; but if (in doing so)
//       client mis-specifies 0 (NOTE: size_type is unsigned, thus
//       can't be negative) as the overriding size, DEFAULT_CAPACITY
//       remains as the value to be used for initial_capacity (this
//       is to ensure no attempt is made at allocating memory that's
//       0 in amount).
// MODIFICATION MEMBER FUNCTIONS for the p_queue class:
//   void push(const value_type& entry, size_type priority)
//     Pre:  (none)
//     Post: A new copy of item with the specified data and priority
//           has been added to the p_queue.
//   void pop()
//     Pre:  size() > 0.
//     Post: The highest priority item has been removed from the
//           p_queue. (If several items have the equal priority,
//           then the implementation may decide which one to remove.)
// CONSTANT MEMBER FUNCTIONS for the p_queue class:
//   size_type size() const
//     Pre:  (none)
//     Post: The return value is the total number of items in the
//           p_queue.
//   value_type front() const
//     Pre:  size() > 0.
//     Post: The return value is the data of the highest priority
//           item in the p_queue, but the p_queue is unchanged.
//           (If several items have equal priority, then the
//           implementation may decide which one to return.)
//   bool empty() const
//     Pre:  (none)
//     Post: The return value is true if the p_queue is empty,
//           otherwise false.
// VALUE SEMANTICS for the p_queue class:
//   Assignments and the copy constructor may be used with p_queue