/*
 * $Revision: 3609 $
 *
 * last checkin:
 *   $Author: beyer $
 *   $Date: 2013-07-01 20:33:08 +0200 (Mon, 01 Jul 2013) $
 ***************************************************************/

/** \file
 * \brief Implementation of binary heap class that allows the
 * decreaseKey operation.
 *
 * \author Karsten Klein
 *
 * \par License:
 * This file is part of the Open Graph Drawing Framework (OGDF).
 *
 * \par
 * Copyright (C)<br>
 * See README.txt in the root directory of the OGDF installation for details.
 *
 * \par
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * Version 2 or 3 as published by the Free Software Foundation;
 * see the file LICENSE.txt included in the packaging of this file
 * for details.
 *
 * \par
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * \par
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 * \see  http://www.gnu.org/copyleft/gpl.html
 ***************************************************************/

#ifdef _MSC_VER
#pragma once
#endif

#ifndef OGDF_BINARY_HEAP2_H
#define OGDF_BINARY_HEAP2_H

#include <ogdf/basic/HeapBase.h>

namespace ogdf {

/**
 * \brief Min-heap priority queue realized by a data array.
 *
 * Heaps store objects that are weighted with costs;
 * the minimal cost object is accessible over
 * member function minRet() and extracted by extractMin().
 *
 * The class uses two template parameters:
 *   - \a key is the key type.
 *   - \a HeapElement is the type of the elements that are stored.
 *
 * HeapObjects can be all types with copy constructor,
 * as copies of inserted elements are created;
 * \a key should be of a type with compare operators.
 * We only allow integer as index/size type; the array index starts with 1.
 *
 * To allow direct access to the underlying array structure
 * in order to minimize decreaseKey() runningtime,
 * a pointer to an integer storage can be provided as input()
 * parameter that will be kept updated with the index position
 * during heap operations.
 *
 * <H3>Running Time</H3>
 * The worst case running times of the methods is given by the following
 * table, where \a n is the current number of elements.
 *
 * <table>
 *   <tr>
 *     <th>method<th>worst-case<th>amortized
 *   </tr><tr>
 *     <td>extractMin()<td>O(n)<td>O(lg(\a n))
 *   </tr><tr>
 *     <td>siftDown()<td>O(lg(\a n))<td>
 *   </tr><tr>
 *     <td>siftUp()<td>O(lg(\a n))<td>
 *   </tr><tr>
 *     <td>minRet()<td>O(1)<td>
 *   </tr><tr>
 *     <td>insert()<td>O(\a n)<td>O(lg(\a n))
 *   </tr>
 * </table>
 */


//to allow directobject adress, a pointer to an integer storage
//can be provided, where the array index is updated by the
//heap class


template <class key, class HeapObject>
class BinaryHeap2 : public HeapBase<key, HeapObject>
{
public:
	//! Creates a binary heap.
	BinaryHeap2(int startSize = 128);

	//copy Constructor, todo
	//BinaryHeap2(const BinaryHeap2& source);

	// Destructor, deletes the heap array.
	virtual ~BinaryHeap2() {
		if (m_heapArray) delete[] m_heapArray;
	}//destructor


	//! Assignment operator.
	const BinaryHeap2& operator=(const BinaryHeap2<key, HeapObject>& rhs);

	//------------------------------------------------------------
	//modification:

	//! Inserts a new element \a obj with priority \a p and pointer for index update.
	void insert(const HeapObject& obj, key& p, int* keyUpdate = 0);

	//! Obtains heap property, only needed if the elements are not inserted by insert method.
	virtual void makeHeap();
	//delete
	//it is not clear how a delete without explicit
	//given heapentry pointer  should behave, e.g. if equal values
	//for objects are allowed

	//! Returns minimum priority element and removes it from the heap.
	// arraySize is decreased if size < 1/3arraySize (amortized runtime O(1))
	HeapObject extractMin();

	//! Decreases priority of an object that is addressed by \a index.
	// use updated m_foreign position index to address entry for decreasekey
	virtual void decreaseKey(int index, key priority);
	//TODO: version mit Aenderungswert statt absolutem Wert

	//--------------------------------------------------------------
	//const access functions

	//! Returns minimum priority element.
	HeapObject minRet() const {return m_heapArray[1].m_object;}

	key getPriority(int index) const
	{
		OGDF_ASSERT( (index > 0) && (index <= HeapBase<key,HeapObject>::m_size) );
		return m_heapArray[index].m_priority;
	}//getPriority

	//! Returns the current size.
	int capacity() const { return m_arraySize; }

	//! Returns the number of stored elements.
	int size() const { return HeapBase<key,HeapObject>::m_size; }

	//! Returns true iff the heap is empty.
	int empty() const { return HeapBase<key,HeapObject>::empty(); }

	//! Reinitializes the data structure.
	/**
	 * Deletes the array and reallocates it with size that was passed at
	 * construction time.
	 */
	void clear();

protected:
	//! Establishes heap property by moving element up in heap if necessary.
	void siftUp(int pos);

	//! Establishes heap property by moving element down in heap if necessary.
	void siftDown(int pos);

	//----------------------------------------------------------
	//modelling the binary tree structure on the data array
	//array position 0 is left empty, positions are from 1..m_size
	//! Array index of parent node.
	int parentIndex(int num)
	{
		OGDF_ASSERT(num>0);
		return num/2;
	}//parent

	//! Array index of left child.
	int leftChildIndex(int num)
	{
		OGDF_ASSERT(num>0);
		return 2*num;
	}//leftChild

	//! Array index of right child.
	int rightChildIndex(int num)
	{
		OGDF_ASSERT(num>0);
		return 2*num+1;
	}//rightChild

	//! Returns true if left child exists.
	bool hasLeft(int num)
	{
		OGDF_ASSERT(num>0);
		return (leftChildIndex(num) <= HeapBase<key,HeapObject>::m_size);
	}

	//! Returns true if right child exists.
	bool hasRight(int num)
	{
		OGDF_ASSERT(num>0);
		return (rightChildIndex(num) <= HeapBase<key,HeapObject>::m_size);
	}

	//----------------------------------------------------------
	//helper functions for internal maintainance
	int arrayBound(int arraySize) {return arraySize+1;}
	int higherArrayBound(int arraySize) {return 2*arraySize+1;}
	int higherArraySize(int arraySize) {return 2*arraySize;}
	int lowerArrayBound(int arraySize) {return arraySize/2+1;}
	int lowerArraySize(int arraySize) {return arraySize/2;}

	void init(int initSize);

private:
	//holding object and priority key
	struct HeapEntry
	{
		key m_priority;
		HeapObject m_object;

		//we maintain positions during operations
		int m_pos;
		int* m_foreignPos; //storage structure given by user

		//! Initializes HeapEntry object.
		HeapEntry() {m_priority = 0;
		m_pos = 0;
		m_foreignPos = 0;
		}

		//! Initializes HeapEntry object with priority.
		/**
		* @param k ist the priority.
		* @param ob is the corresponding HeapObject.
		*/
		HeapEntry(key k, const HeapObject& ob) {m_priority = k; m_object = ob;
		m_foreignPos = 0;
		//m_pos = ob.m_pos;
		}

		//! Initializes HaepEntry object with priority.
		/**
		* @param k ist the priority.
		* @param ob is the corresponding HeapObject.
		* @param pos is the position of the object within the array.
		* @param fp is a pointer to the index.
		*/
		HeapEntry(key k, const HeapObject& ob, int pos, int* fp)
		{
			m_priority = k;
			m_object = ob;
			if (fp == 0) m_foreignPos = 0;
			else m_foreignPos = fp;
			m_pos = pos;
		}
	};

	HeapEntry* m_heapArray; //dynamically maintained array of heapentries

	//in addition to m_size, the inherited number of objects from class HeapBase,
	//we store the actual size of the array, valid array object positions
	//are from 1 to m_size
	int m_arraySize; //current size of the heap

	int m_startSize; //(decide: optionally??) used to check reallocation bound

};//BinaryHeap2



//**************************************************************
//implementation
//**************************************************************


//**************************************************************
//constructor and initialization
template <class key, class HeapObject>
BinaryHeap2<key, HeapObject>::BinaryHeap2(int startSize)
: HeapBase<key, HeapObject>()
{
	init(startSize);
}//constructor


template <class key, class HeapObject>
void BinaryHeap2<key, HeapObject>::init(int initSize)
{
	//create an array of HeapEntry Elements
	m_arraySize = initSize;
	m_heapArray = new HeapEntry[arrayBound(m_arraySize)]; //start at 1

	m_startSize = initSize;

	HeapBase<key,HeapObject>::m_size = 0;
}


template <class key, class HeapObject>
void BinaryHeap2<key, HeapObject>::clear()
{
	if (m_heapArray) delete[] m_heapArray;
	init(m_startSize);
}


//**************************************************************
//element shifting operations
//restore heap property by finding correct position for object
//at position pos on higher levels, pos is given as array index (1..m_size)
//updates array index values
template <class key, class HeapObject>
void BinaryHeap2<key, HeapObject>::siftUp(int pos)
{
	OGDF_ASSERT( (pos > 0) && (pos <= HeapBase<key,HeapObject>::m_size) )

		if (pos == 1)
		{
			m_heapArray[1].m_pos = 1;
			if (m_heapArray[1].m_foreignPos != 0) //address is defined
				*(m_heapArray[1].m_foreignPos) = 1;
			return;//nothing to do
		}

		HeapEntry tempEntry = m_heapArray[pos];
		int run = pos;
		while ( (parentIndex(run) >= 1) &&
			(m_heapArray[parentIndex(run)].m_priority > tempEntry.m_priority) )
		{
			m_heapArray[run] = m_heapArray[parentIndex(run)];
			if (m_heapArray[run].m_foreignPos != 0) *(m_heapArray[run].m_foreignPos) = run;
			run = parentIndex(run);
		}//while

		m_heapArray[run] = tempEntry;
		m_heapArray[run].m_pos = run;
		if (m_heapArray[run].m_foreignPos != 0) *(m_heapArray[run].m_foreignPos) = run;


}//siftup


//restore heap property by finding correct position for object
//at position pos on lower levels, updates array index values
template <class key, class HeapObject>
void BinaryHeap2<key, HeapObject>::siftDown(int pos)
{
	OGDF_ASSERT( (pos > 0) && (pos <= HeapBase<key,HeapObject>::m_size) );

	if (pos >= int(HeapBase<key,HeapObject>::m_size/2)+1)
	{
		m_heapArray[pos].m_pos = pos;
		if (m_heapArray[pos].m_foreignPos != 0) *(m_heapArray[pos].m_foreignPos) = pos;
		return; //leafs cant move down
	}//if leaf

	key sPrio = getPriority(pos);
	int sIndex = pos;

	if (hasLeft(pos) && (getPriority(leftChildIndex(pos)) < sPrio) )
	{
		sIndex = leftChildIndex(pos);
		sPrio = getPriority(leftChildIndex(pos));
	}//if left child smaller
	if (hasRight(pos) && (getPriority(rightChildIndex(pos)) < sPrio) )
	{
		sIndex = rightChildIndex(pos);
		sPrio = getPriority(rightChildIndex(pos));
	}//if right child smaller

	if (sIndex != pos)
	{
		HeapEntry tempEntry = m_heapArray[pos];
		m_heapArray[pos] = m_heapArray[sIndex];
		m_heapArray[sIndex] = tempEntry;

		//update both index entries
		m_heapArray[pos].m_pos = pos;
		if (m_heapArray[pos].m_foreignPos != 0) *(m_heapArray[pos].m_foreignPos) = pos;
		m_heapArray[sIndex].m_pos = sIndex;
		if (m_heapArray[sIndex].m_foreignPos != 0) *(m_heapArray[sIndex].m_foreignPos) = sIndex;

		siftDown(sIndex); //TODO: dont use recursion
	}//if sift necessary
	else  //update in case of new elements (non-insert)
	{
		m_heapArray[pos].m_pos = pos;
		if (m_heapArray[pos].m_foreignPos != 0) *(m_heapArray[pos].m_foreignPos) = pos;
	}//else
}//siftdown


template <class key, class HeapObject>
void BinaryHeap2<key, HeapObject>::makeHeap()
{
	//only needed if insertion is not done over insert
	//(if we allow array parameter in constructor)
	for (int i=HeapBase<key,HeapObject>::m_size/2; i > 0; i--)
		siftDown(i);
}//makeheap


template <class key, class HeapObject>
void BinaryHeap2<key, HeapObject>::decreaseKey(int index, key priority)
{
	HeapEntry& he = m_heapArray[index];

	//check if error value
	if (he.m_priority < priority) OGDF_THROW_PARAM(AlgorithmFailureException, afcIllegalParameter);

	he.m_priority = priority;
	siftUp(index);

}//decreaseKey


//extract the minimum priority object and reallocate array if size < 1/3 arraysize
template <class key, class HeapObject>
HeapObject BinaryHeap2<key, HeapObject>::extractMin()
{
	OGDF_ASSERT((!HeapBase<key,HeapObject>::empty()));

	HeapEntry tempEntry = m_heapArray[1]; //save minimum object

	HeapBase<key,HeapObject>::m_size--;

	if (HeapBase<key,HeapObject>::m_size > 0)
	{
		m_heapArray[1] = m_heapArray[HeapBase<key,HeapObject>::m_size+1]; //old last leaf

		//check if reallocation is possible
		if ((HeapBase<key,HeapObject>::m_size < (m_arraySize/3)) && (m_arraySize > 2*m_startSize-1))
		{
			HeapEntry* tempHeap = new HeapEntry[lowerArrayBound(m_arraySize)];
			for (int i = 1; i <= HeapBase<key,HeapObject>::m_size ; i++)
				tempHeap[i] = m_heapArray[i];
			delete[] m_heapArray;
			m_heapArray = tempHeap;
			m_arraySize = lowerArraySize(m_arraySize);

		}//if small enough

		//restore tree by sifting down old leaf
		siftDown(1);
	}//if not empty

	return tempEntry.m_object;

}//extractMin


//place a copy of the given input element in the queue, doubles
//array size if necessary
template <class key, class HeapObject>
void BinaryHeap2<key, HeapObject>::insert(const HeapObject& ho, key& priority, int* keyUpdate)
{
	OGDF_ASSERT((HeapBase<key,HeapObject>::m_size) < m_arraySize);
	HeapBase<key,HeapObject>::m_size++;
	//check if the array size has to be adjusted
	if (HeapBase<key,HeapObject>::m_size == m_arraySize)
	{
		HeapEntry* tempHeap = new HeapEntry[higherArrayBound(m_arraySize)];
		for (int i = 1; i <= m_arraySize ; i++) //last one is not occupied yet
			tempHeap[i] = m_heapArray[i];
		delete[] m_heapArray;
		m_heapArray = tempHeap;
		m_arraySize = higherArraySize(m_arraySize);

	}//if array full

	//now insert object and reestablish heap property
	m_heapArray[HeapBase<key,HeapObject>::m_size] = HeapEntry(priority, ho, HeapBase<key,HeapObject>::m_size, keyUpdate);

	siftUp(HeapBase<key,HeapObject>::m_size);

}//insert



template <class key, class HeapObject>
const BinaryHeap2<key, HeapObject>& BinaryHeap2<key, HeapObject>::operator=(const BinaryHeap2<key, HeapObject>& rhs)
{
	if (this != &rhs)
	{
		if (m_heapArray && !(m_arraySize == rhs.m_arraySize))
		{
			delete[] m_heapArray;
			m_heapArray = 0;
		}//if

		if (!m_heapArray)
			m_heapArray = new HeapEntry[arrayBound(rhs.m_arraySize)]; //start at 1

		OGDF_ASSERT(m_heapArray);

		HeapBase<key,HeapObject>::m_size = rhs.m_size;

		m_startSize = rhs.m_startSize;
		m_arraySize = rhs.m_arraySize;

		for (int i = 1; i <= HeapBase<key,HeapObject>::m_size ; i++)
			m_heapArray[i] = rhs.m_heapArray[i];

	}//if not self
	return *this;
}



}//namespace ogdf

#endif
