/******************************************************************************************[Heap.h]
MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson

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The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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**************************************************************************************************/

#ifndef Heap_h
#define Heap_h

#include "Vec.h"

//=================================================================================================
// A heap implementation with support for decrease/increase key.

namespace minisat2 {

template<class Comp>
class Heap
{
		Comp     lt;
		vec<int> heap;     // heap of ints
		vec<int> indices;  // int -> index in heap

		// Index "traversal" functions
		static inline int left ( int i ) { return i*2+1; }
		static inline int right ( int i ) { return ( i+1 ) *2; }
		static inline int parent ( int i ) { return ( i-1 ) >> 1; }


		inline void percolateUp ( int i )
		{
			int x = heap[i];
			while ( i != 0 && lt ( x, heap[parent ( i ) ] ) )
			{
				heap[i]          = heap[parent ( i ) ];
				indices[heap[i]] = i;
				i                = parent ( i );
			}
			heap   [i] = x;
			indices[x] = i;
		}


		inline void percolateDown ( int i )
		{
			int x = heap[i];
			while ( left ( i ) < heap.size() )
			{
				int child = right ( i ) < heap.size() && lt ( heap[right ( i ) ], heap[left ( i ) ] ) ? right ( i ) : left ( i );
				if ( !lt ( heap[child], x ) ) break;
				heap[i]          = heap[child];
				indices[heap[i]] = i;
				i                = child;
			}
			heap   [i] = x;
			indices[x] = i;
		}


		bool heapProperty ( int i ) const
		{
			return i >= heap.size()
			       || ( ( i == 0 || !lt ( heap[i], heap[parent ( i ) ] ) ) && heapProperty ( left ( i ) ) && heapProperty ( right ( i ) ) );
		}


	public:
		Heap ( const Comp& c ) : lt ( c ) { }

		int  size ()          const { return heap.size(); }
		bool empty ()          const { return heap.size() == 0; }
		bool inHeap ( int n )     const { return n < indices.size() && indices[n] >= 0; }
		int  operator[] ( int index ) const { assert ( index < heap.size() ); return heap[index]; }

		void decrease ( int n ) { assert ( inHeap ( n ) ); percolateUp ( indices[n] ); }

		// RENAME WHEN THE DEPRECATED INCREASE IS REMOVED.
		void increase_ ( int n ) { assert ( inHeap ( n ) ); percolateDown ( indices[n] ); }


		void insert ( int n )
		{
			indices.growTo ( n+1, -1 );
			assert ( !inHeap ( n ) );

			indices[n] = heap.size();
			heap.push ( n );
			percolateUp ( indices[n] );
		}


		int  removeMin()
		{
			int x            = heap[0];
			heap[0]          = heap.last();
			indices[heap[0]] = 0;
			indices[x]       = -1;
			heap.pop();
			if ( heap.size() > 1 ) percolateDown ( 0 );
			return x;
		}


		void clear ( bool dealloc = false )
		{
			for ( int i = 0; i < heap.size(); i++ )
				indices[heap[i]] = -1;
#ifdef NDEBUG
			for ( int i = 0; i < indices.size(); i++ )
				assert ( indices[i] == -1 );
#endif
			heap.clear ( dealloc );
		}


		// Fool proof variant of insert/decrease/increase
		void update ( int n )
		{
			if ( !inHeap ( n ) )
				insert ( n );
			else
			{
				percolateUp ( indices[n] );
				percolateDown ( indices[n] );
			}
		}


		// Delete elements from the heap using a given filter function (-object).
		// *** this could probaly be replaced with a more general "buildHeap(vec<int>&)" method ***
		template <class F>
		void filter ( const F& filt )
		{
			int i,j;
			for ( i = j = 0; i < heap.size(); i++ )
				if ( filt ( heap[i] ) )
				{
					heap[j]          = heap[i];
					indices[heap[i]] = j++;
				}
				else
					indices[heap[i]] = -1;

			heap.shrink ( i - j );
			for ( int i = heap.size() / 2 - 1; i >= 0; i-- )
				percolateDown ( i );

			assert ( heapProperty() );
		}


		// DEBUG: consistency checking
		bool heapProperty() const
		{
			return heapProperty ( 1 );
		}


		// COMPAT: should be removed
		void setBounds ( int n ) { }
		void increase ( int n ) { decrease ( n ); }
		int  getmin ()      { return removeMin(); }

};

}
//=================================================================================================
#endif
