old_prio_queue.cpp

#include <cassert>
#include <cstdio>

#define PARENT(x) (((x) - 1) >> 1)
#define LEFTCHILD(x) (((x) << 1) + 1)
#define RIGHTCHILD(x) (((x) + 1) << 1)

template<typename T>
class CPriQueue
{
    public:
		typedef int pos;

	public:
		CPriQueue();
		CPriQueue(const CPriQueue& q);
		~CPriQueue();

	public:
		CPriQueue& operator =(const CPriQueue& q);
		void BuildHeap(const T ary[], int count);
		void Insert(const T& ele);
		T ExtractMin();
		inline T Min() const;
		inline int GetCount() const;
		inline bool IsEmpty() const;
		inline bool IsFull() const;
		pos Find(const T& ele) const;
		void DecreaseKey(pos p, unsigned int det);
		void IncreaseKey(pos p, unsigned int det);
		void Delete(pos p);

		// diagnostic interface
		#if _DEBUG
		void DgPrint();
		#endif

	private:
		void PercolateUp(int i, const T& ele);
		void PercolateDown(int i, const T& ele);

	private:
		enum{INI_CAPCITY = 50, NOT_FOUND = -1};
		T* m_pHeap;
		int m_capcity;
		int m_count;
};


template<typename T>
CPriQueue<T>::CPriQueue() : m_count(0)
{
	m_pHeap = new T[INI_CAPCITY];
	assert(m_pHeap != NULL);
	m_capcity = INI_CAPCITY;
}


template<typename T>
CPriQueue<T>::CPriQueue(const CPriQueue& q) : m_capcity(q.m_capcity),
											  m_count(q.m_count)
{
	m_pHeap = new T[m_capcity];
	assert(m_pHeap != NULL);	

	// the element may have internal handle pointing to the extra data outside
	// assume that the object already overloaded operator =
	for (int i = 0; i < m_count; ++i)
	{
		m_pHeap[i] = q.m_pHeap[i];
	}
}


template<typename T>
CPriQueue<T>::~CPriQueue()
{
	if (m_pHeap != NULL)
	{
		delete [] m_pHeap;
		m_pHeap = NULL;
		m_capcity = 0;
		m_count = 0;
	}
}


template<typename T>
CPriQueue<T>& CPriQueue<T>::operator =(const CPriQueue& q)
{
	if (m_capcity < q.m_count)
	{
		// need to expand
		assert(false);
	}

	m_count = q.m_count

	for (int i = 0; i < m_count; ++i)
	{
		m_pHeap[i] = q.m_pHeap[i];
	}	

	return *this;
}



template<typename T>
void CPriQueue<T>::Insert(const T& ele)
{
	if (IsFull())
	{
		// Logs error or expands capcity of the heap
		assert(false);
	}

	// new element may violate heap property
	PercolateUp(m_count, ele);
	++m_count;
}


/*
	Description:
		Adjusts the specific element which may violate the heap property
		upward.
	Parameters:
		i[in] - the position in the heap of the specific element. 
		ele[in] - a copy of the element. It's used to make the function more
		efficient. Do not have this parameter refered to the element directly.
		It may possible change the value of the ele while adjusting.
	Return Value:
		none
*/
template<typename T>
void CPriQueue<T>::PercolateUp(int i, const T& ele)
{
	for (int p = PARENT(i); ele < m_pHeap[p]; p = PARENT(p))
	{
		// reaches the root
		if (0 == i)
		{
			break;
		}

		m_pHeap[i] = m_pHeap[p];
		i = p;
	}

	m_pHeap[i] = ele;
}


template<typename T>
T CPriQueue<T>::ExtractMin()
{
	assert(!IsEmpty());

	T ret(m_pHeap[0]);

	// new root violates the heap property
	PercolateDown(0, m_pHeap[--m_count]);
	return ret;
}

/*
	Description:
		It is Similar to the function PercolateUp but downward.
	Parameters:
		i[in] - the position in the heap of the specific element. 
		ele[in] - the same as in PercolateUp
	Return Value:
		none
*/
template<typename T>
void CPriQueue<T>::PercolateDown(int i, const T& ele)
{
	for (; LEFTCHILD(i) < m_count;)
	{
		// the node may have only left child
		int iL = LEFTCHILD(i);
		int iR = RIGHTCHILD(i);
		int iMin = iR < m_count ? (m_pHeap[iL] < m_pHeap[iR] ? iL : iR) : iL;		

		if (m_pHeap[iMin] < ele)
		{
			m_pHeap[i] = m_pHeap[iMin];
			i = iMin;
		} 
		else
		{
			break;
		}
	}

	m_pHeap[i] = ele;
}


template<typename T>
inline T CPriQueue<T>::Min() const
{
	assert(!IsEmpty());
	return m_pHeap[0];	
}


template<typename T>
inline int CPriQueue<T>::GetCount() const
{
	return m_count;
}


template<typename T>
inline bool CPriQueue<T>::IsEmpty() const
{
	return 0 == m_count ? true : false;
}


template<typename T>
inline bool CPriQueue<T>::IsFull() const
{
	return m_capcity == m_count ? true : false;
}


/*
	Description:
		Returns the position of the specific element to be found. The function
		takes O(N) time
	Parameters:
		ele[in] - the element we search for
	Return Value:
		The function returns NOT_FOUND if the specific element is not found
		otherwise the return value indicates the position of the element
*/
template<typename T>
typename CPriQueue<T>::pos CPriQueue<T>::Find(const T& ele) const
{
	pos index = NOT_FOUND;

	for (int i = 0; i < m_count; ++i)
	{
		if (m_pHeap[i] == ele)
		{
			index = i;
			break;
		}
	}

	return index;
}


template<typename T>
void CPriQueue<T>::DecreaseKey(pos p, unsigned int det)
{
	assert(p >= 0);

	m_pHeap[p] -= det;
	T newEle(m_pHeap[p]);

	// adjusts the order property
	PercolateUp(p, newEle);
}


template<typename T>
void CPriQueue<T>::IncreaseKey(pos p, unsigned int det)
{
	assert(p >= 0);

	m_pHeap[p] += det;
	T newEle(m_pHeap[p]);

	PercolateDown(p, newEle);	
}


template<typename T>
void CPriQueue<T>::Delete(pos p)
{
	assert(p >= 0);

	int det = m_pHeap[p] - m_pHeap[0] + 1;
	DecreaseKey(p, det);
	ExtractMin();
}


/*
	Description:
		Builds up the heap from an array
	Parameters:
		ary[in] - the array contains elements
		count[in] - indicates the counts of the elements in array
	Return Value:
		none
*/
template<typename T>
void CPriQueue<T>::BuildHeap(const T ary[], int count)
{
	assert(m_capcity >= count);

	for (int i = 0; i < count; ++i)
	{
		m_pHeap[i] = ary[i];
	}

	m_count = count;

	for (int i = PARENT(count - 1); i >= 0; --i)
	{
		T eleMov(m_pHeap[i]);
		PercolateDown(i, eleMov);
	}
}


#if _DEBUG
template<typename T>
void CPriQueue<T>::DgPrint()
{
	for (int i = 0; i < m_count; ++i)
	{
		wprintf_s(L"%d\t", m_pHeap[i]);
	}

	wprintf_s(L"\n");
}
#endif