priorityqueue.h

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      if (!v_d[i]->eq(*compare_queue_a.v_d[i])) {
	are_equal = false;
      }
    }
    else {
      if (v_d[i] != compare_queue_a.v_d[i]) {
	are_equal = false;
      }
    }
  }
  
  // return a value representing if they are equivalent
  //
  return are_equal;
}

//-------------------------------------------------------------------------
//
// required memory management methods
//
//-------------------------------------------------------------------------

// method: clear
//
// arguments: 
// Integral::CMODE cmode_a: (input) clear mode
//  
// return: a boolean value indicating status
//
// this method clears the contents of the list by the setting of cmode_a
//
//  enum CMODE { RETAIN = 0, RESET, RELEASE, FREE, DEF_CMODE = RESET };
//
// RETAIN: call clear with RETAIN on each element in the queue
//
// RESET: clear the structure but don't necessarily delete memory
//
// RELEASE: clear the structure and release memory
//
// FREE: clear the structure and release memory
//
// Programming hint:
//
// use the clear() method to manage the memory of the objects going
// into the queue.
// particular useful when queue is in USER mode. Caution the object
// you place into queue must have a clear method that meets the
// requirements of the IFC clear method.
//
//
template<class TObject>
boolean PriorityQueue<TObject>::clear(Integral::CMODE cmode_a) {

  // if the cmode_a is RETAIN or FREE, call clear(cmode_a) method for
  // each element
  //  
  if ((cmode_a == Integral::RETAIN) || (cmode_a == Integral::FREE)) {

    // loop over all elements
    //
    for (long i = 0; i < (long)length_d; i++) {
      v_d[i]->clear(cmode_a);
    }
  }

  // if the cmode_a is RESET, clear the structure but don't 
  // necessarily delete memory
  //    
  if (cmode_a == Integral::RESET) {
    setLength(0);
  }
  
  // if the cmode_a is RELEASE or FREE, clear the structure and
  // release memory.
  //
  else if ((cmode_a == Integral::RELEASE) || (cmode_a == Integral::FREE)) {

    // free memory -- the setCapacity call will actually release it.
    //
    setCapacity(0);
    length_d = 0;
  }
  
  // exit gracefully
  //
  return true;
}

//------------------------------------------------------------------------
//
// class-specific public methods:
//  get and set methods
//
//------------------------------------------------------------------------

// method: setLength
// 
// arguments:
//  long length: (input) new length
//  boolean preserve_values: (input) should we save the memory
//   
// return: a boolean value indicating status
//
// this method sets the length, or number of valid elements
//
template<class TObject>
boolean PriorityQueue<TObject>::setLength(long length_a, boolean preserve_values_a) {

  // check arguments
  // 
  if (length_a < 0) {
    return Error::handle(name(), L"setLength", Error::ARG, __FILE__, __LINE__);
  }
  
  // if new length is greater than capacity, call setCapacity
  //
  if (length_a > capacity_d) {
    if (!setCapacity(length_a, preserve_values_a)) {
      return Error::handle(name(), L"setLength", Error::NOMEM,
			   __FILE__, __LINE__);
    }
  }

  // set new length
  // 
  length_d = length_a;
    
  // exit gracefully
  // 
  return true;
}

// method: setCapacity
// 
// arguments:
//  long capacity: (input) new capacity
//  boolean preserve_values: (input) should we save the memory
//   
// return: a boolean value indicating status
//
// this method sets the capacity, which is the maximum number of elements
// this queue can hold.
//
template<class TObject>
boolean PriorityQueue<TObject>::setCapacity(long capacity_a,
				     boolean preserve_values_a) {
  
  // capacity_a < 0: error
  // 
  if (capacity_a < 0) {
    return Error::handle(name(), L"setCapacity",
			 Error::ARG, __FILE__, __LINE__);
  }

  // capacity_a = capacity_d: done
  //
  else if (capacity_a == capacity_d) {
    return true;
  }

  // capacity_a == 0 (and length_d == 0): just delete memory
  //
  else if (capacity_a == 0) {
    
    // delete the old memory
    //
    if (v_d != (TObject**)NULL) {
      if (alloc_d == SYSTEM) {
	for (long i=0; i < (long)length_d; i++) {
	  if (v_d[i] != (TObject*)NULL) {
	    delete v_d[i];
	    v_d[i] = (TObject*)NULL;
	  }
	}
      }
      delete [] v_d;
      v_d = (TObject**)NULL;
    }
  }
  
  // capacity_a >= length_d: we will need to allocate memory and/or
  // transfer data.
  //
  else {

    // allocate a new chunk of memory
    //
    TObject** new_mem = new TObject*[capacity_a];
    if (new_mem == (TObject**)NULL) {
      return Error::handle(name(), L"setCapacity", Error::NOMEM,
			   __FILE__, __LINE__);
    }

    // initialize the memory
    //
    for (long i=0; i < (long)capacity_a; i++) {
      new_mem[i] = (TObject*)NULL;
    }
    
    // if there are valid elements and we need to preserve them
    //
    if (((long)length_d > 0) && preserve_values_a) {
      for (long i = 0; i < (long)length_d; i++) {
	new_mem[i] = accessByMode(v_d[i]);
      }
    }
    
    // delete the old memory
    //
    if (v_d != (TObject**)NULL) {
      if (alloc_d == SYSTEM) {
	for (long i=0; i < (long)length_d; i++) {
	  if (v_d[i] != (TObject*)NULL) {
	    delete v_d[i];
	    v_d[i] = (TObject*)NULL;
	  }
	}
      }      
      delete [] v_d;
      v_d = (TObject**)NULL;
    }
    
    // assign the pointer to the new memory
    //
    v_d = new_mem;
  }
  
  // set the new capacity
  //
  capacity_d = capacity_a;

  // exit gracefully
  //
  return true;
}

//---------------------------------------------------------------------------
//
// class-specific public methods:
//  queue property methods
//
//---------------------------------------------------------------------------

// method: push
// 
// arguments:
//  TObject* item: (input) item to be inserted
//  COMPARE_FUNC comp_func: (input) priority queue comparison function
//   
// return: a boolean value indicating status
//
// this method inserts an item into the queue
//
template<class TObject>
boolean PriorityQueue<TObject>::push(TObject* item_a,
				     COMPARE_FUNC comp_func_a) {

  // declare local variables
  //
  TObject* new_obj = (TObject*)NULL;

  // mode: SYSTEM
  //  make a copy of the element
  //
  if (alloc_d == SYSTEM) {
    new_obj = new TObject(*item_a);
  }

  // mode: USER
  //  make a copy of the pointer to the item
  //
  else {
    new_obj = item_a;
  }
  
  // increase the size of the heap by one
  //
  setLength((long)length_d + 1);

  // propagate the item up the heap until the heap properties are met
  //
  long i = (long)length_d - 1;
  while ((i > 0) &&
	 (comp_func_a(v_d[parent(i)], new_obj) == Integral::LESSER)) {
    v_d[i] = v_d[parent(i)];
    i = parent(i);
  }
  v_d[i] = new_obj;

  // exit gracefully
  //
  return true;
}

// method: pop
// 
// arguments:
//  TObject* item: (output) item to be removed
//   
// return: a boolean value indicating status
//
// this method removes the maximum item from the queue
//
template<class TObject>
TObject* PriorityQueue<TObject>::pop(TObject* item_a) {

  // declare local variables
  //
  TObject* ptr = (TObject*)NULL;
  
  // when in SYSTEM mode the item passed in should not be
  // null, if we are in USER mode the item should be null
  //
  if (((alloc_d == SYSTEM) && (item_a == (TObject*)NULL)) ||
      ((alloc_d == USER) && (item_a != (TObject*)NULL))) {
    Error::handle(name(), L"remove", ERR, __FILE__, __LINE__);
    return (TObject*)NULL;
  }
  
  // check for heap size violations
  //
  if (!isEmpty()) {

    // retrieve the maximum item form the heap
    //
    ptr = v_d[0];

    // mode: SYSTEM
    //
    if (alloc_d == SYSTEM) {

      // make a copy of the object
      //
      item_a->assign(*ptr);

      // delete the reference to the object      
      //
      delete ptr;
    }
    
    // mode: USER
    //
    else {
      
      // assign the pointer to the item
      //
      item_a = ptr;
    }
    
    // remove the maximum item and reorganize the heap
    //
    v_d[0] = v_d[(long)length_d - 1];
    setLength((long)length_d - 1);
    heapify(0);
    
    // return a pointer to the object (so that the return value can
    // be compared)
    //
    return item_a;
  }

  // nothing in queue, return null
  //
  return (TObject*)NULL;  
}

// method: top
// 
// arguments:
//  TObject* item: (output) item to be removed
//   
// return: a boolean value indicating status
//
// this method removes the maximum item from the queue
//
template<class TObject>
const TObject* PriorityQueue<TObject>::top() const {

  // check for heap size violations
  //
  if (isEmpty()) {
    Error::handle(name(), L"top", Error::ARG, __FILE__, __LINE__);
    return (TObject*)NULL;
  }

  // return the maximum item in the heap
  //
  return v_d[0];
}

// method: top
// 
// arguments:
//  TObject* item: (output) item to be removed
//   
// return: a boolean value indicating status
//
// this method removes the maximum item from the queue
//
template<class TObject>
TObject* PriorityQueue<TObject>::top() {

  // check for heap size violations
  //
  if (isEmpty()) {
    Error::handle(name(), L"top", Error::ARG, __FILE__, __LINE__);
    return (TObject*)NULL;
  }

  // return the maximum item in the heap
  //
  return v_d[0];
}

//---------------------------------------------------------------------------
//
// heap manipulation methods
//
//---------------------------------------------------------------------------

// method: compare
// 
// arguments:
//  TObject* item1: (input) first item to compare
//  TObject* item2: (input) second item to compare
//   
// return: an enum indicating comparison status
//
// method compares the input items
//
template<class TObject>
Integral::COMPARE PriorityQueue<TObject>::compare(TObject* item1_a,
						  TObject* item2_a) {

  // check if item1 is greater than item2
  //
  if (*item1_a > *item2_a) {
    return Integral::GREATER;
  }

  // check if item1 is less than item2
  //
  if (*item1_a < *item2_a) {
    return Integral::LESSER;
  }

  // if we made it this far then the item must be equal
  //
  return Integral::EQUAL;
}
 
// method: heapify
// 
// arguments:
//  long index: (input) index at which o start the heapify process
//  COMPARE_FUNC comp_func: (input) priority queue comparison function
//   
// return: a boolean value indicating status
//
// this method verifies that the underlying array obeys the heap property
//
template<class TObject>
boolean PriorityQueue<TObject>::heapify(long index_a,
					COMPARE_FUNC comp_func_a) {

  // declare local variables
  //
  TObject* tmp = (TObject*)NULL;

  // get the children of the index
  //
  long l = left(index_a);
  long r = right(index_a);

  // assume the current index is the largest
  //
  long largest = index_a;

  // check if the left child is larger
  //
  if ((l < (long)length_d) &&
      (comp_func_a(v_d[l], v_d[index_a]) == Integral::GREATER)) {
    largest = l;
  }

  // check if the right child is larger
  //
  if ((r < (long)length_d) &&
      (comp_func_a(v_d[r], v_d[largest]) == Integral::GREATER)) {
    largest = r;
  }

  // check if the heap property is violated
  //
  if (largest != index_a) {

    // exchange
    //
    tmp = v_d[largest];
    v_d[largest] = v_d[index_a];
    v_d[index_a] = tmp;

    // recursively reorder the heap
    //
    heapify(largest);
  }
  
  // exit gracefully
  //
  return true;
}

// method: buildHeap
// 
// arguments: none
//   
// return: a boolean value indicating status
//
// this method builds a heap out of the underlying array
//
template<class TObject>
boolean PriorityQueue<TObject>::buildHeap() {

  // build the heap using the heapify routine
  //
  long size = (long)length_d - 1;
  for (long i=size/2; i >= 0; i--) {
    heapify(i);
  }
  
  // exit gracefully
  //
  return true;
}

// method: heapSort
// 
// arguments: none
//   
// return: a boolean value indicating status
//
// this method sorts the elements in the heap
//
template<class TObject>
boolean PriorityQueue<TObject>::heapSort() {

  // declare local variables
  //
  long size = (long)length_d;
  TObject* tmp = (TObject*)NULL;

  // construct the heap out of the existing elements
  //
  buildHeap();

  // loop over the elements and sort them as we move along
  //
  for (long i=(long)length_d - 1; i >= 1; i--) {

    // exchange
    //
    tmp = v_d[0];
    v_d[0] = v_d[i];
    v_d[i] = tmp;

    // reduce the size of the heap and reorder
    //
    setLength((long)length_d - 1);
    heapify(0);
  }

  // reset the length after we are done
  //
  setLength(size);
  
  // exit gracefully
  //
  return true;
}

// method: accessByMode
// 
// arguments:
//   TObject* item: (input) input item to access by mode
//   
// return: input item accessed by mode
//
// this method accesses the input element via the access mode
//
template<class TObject>
TObject* PriorityQueue<TObject>::accessByMode(TObject* item_a) {

  // declare local variables
  //
  TObject* new_obj = (TObject*)NULL;

  // access by mode
  //
  if (alloc_d == USER) {
    new_obj = item_a;
  }
  else {
    new_obj = new TObject(*item_a);
  }

  // return the item by mode
  //
  return new_obj;
}

// end of include file
//
#endif