// Heap implementation -*- C++ -*-

// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library 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.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

/*
 *
 * Copyright (c) 1994
 * Hewlett-Packard Company
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Hewlett-Packard Company makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 *
 * Copyright (c) 1997
 * Silicon Graphics Computer Systems, Inc.
 *
 * Permission to use, copy, modify, distribute and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appear in all copies and
 * that both that copyright notice and this permission notice appear
 * in supporting documentation.  Silicon Graphics makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 */

/** @file stl_heap.h
 *  This is an internal header file, included by other library headers.
 *  You should not attempt to use it directly.
 */

#ifndef _STL_HEAP_H
#define _STL_HEAP_H 1

namespace std
{

  // Heap-manipulation functions: push_heap, pop_heap, make_heap, sort_heap.

  template<typename _RandomAccessIterator, typename _Distance, typename _Tp>
    void 
    __push_heap(_RandomAccessIterator __first,
		_Distance __holeIndex, _Distance __topIndex, _Tp __value)
    {
      _Distance __parent = (__holeIndex - 1) / 2;
      while (__holeIndex > __topIndex && *(__first + __parent) < __value) {
	*(__first + __holeIndex) = *(__first + __parent);
	__holeIndex = __parent;
	__parent = (__holeIndex - 1) / 2;
      }    
      *(__first + __holeIndex) = __value;
    }

  /**
   *  @brief  Push an element onto a heap.
   *  @param  first  Start of heap.
   *  @param  last   End of heap + element.
   *  @ingroup heap
   *
   *  This operation pushes the element at last-1 onto the valid heap over the
   *  range [first,last-1).  After completion, [first,last) is a valid heap.
  */
  template<typename _RandomAccessIterator>
    inline void 
    push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
    {
      typedef typename iterator_traits<_RandomAccessIterator>::value_type
	  _ValueType;
      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
	  _DistanceType;

      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)
      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)

      std::__push_heap(__first, _DistanceType((__last - __first) - 1), _DistanceType(0), 
		       _ValueType(*(__last - 1)));
    }

  template<typename _RandomAccessIterator, typename _Distance, typename _Tp, 
	    typename _Compare>
    void
    __push_heap(_RandomAccessIterator __first, _Distance __holeIndex,
		_Distance __topIndex, _Tp __value, _Compare __comp)
    {
      _Distance __parent = (__holeIndex - 1) / 2;
      while (__holeIndex > __topIndex && __comp(*(__first + __parent), __value)) {
	*(__first + __holeIndex) = *(__first + __parent);
	__holeIndex = __parent;
	__parent = (__holeIndex - 1) / 2;
      }
      *(__first + __holeIndex) = __value;
    }

  /**
   *  @brief  Push an element onto a heap using comparison functor.
   *  @param  first  Start of heap.
   *  @param  last   End of heap + element.
   *  @param  comp   Comparison functor.
   *  @ingroup heap
   *
   *  This operation pushes the element at last-1 onto the valid heap over the
   *  range [first,last-1).  After completion, [first,last) is a valid heap.
   *  Compare operations are performed using comp.
  */
  template<typename _RandomAccessIterator, typename _Compare>
    inline void 
    push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
	      _Compare __comp)
    {
      typedef typename iterator_traits<_RandomAccessIterator>::value_type
	  _ValueType;
      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
	  _DistanceType;

      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)

      std::__push_heap(__first, _DistanceType((__last - __first) - 1), _DistanceType(0), 
		       _ValueType(*(__last - 1)), __comp);
    }

  template<typename _RandomAccessIterator, typename _Distance, typename _Tp>
    void 
    __adjust_heap(_RandomAccessIterator __first, _Distance __holeIndex,
		  _Distance __len, _Tp __value)
    {
      _Distance __topIndex = __holeIndex;
      _Distance __secondChild = 2 * __holeIndex + 2;
      while (__secondChild < __len) {
	if (*(__first + __secondChild) < *(__first + (__secondChild - 1)))
	  __secondChild--;
	*(__first + __holeIndex) = *(__first + __secondChild);
	__holeIndex = __secondChild;
	__secondChild = 2 * (__secondChild + 1);
      }
      if (__secondChild == __len) {
	*(__first + __holeIndex) = *(__first + (__secondChild - 1));
	__holeIndex = __secondChild - 1;
      }
      std::__push_heap(__first, __holeIndex, __topIndex, __value);
    }

  template<typename _RandomAccessIterator, typename _Tp>
    inline void 
    __pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
	       _RandomAccessIterator __result, _Tp __value)
    {
      typedef typename iterator_traits<_RandomAccessIterator>::difference_type _Distance;
      *__result = *__first;
      std::__adjust_heap(__first, _Distance(0), _Distance(__last - __first), __value);
    }

  /**
   *  @brief  Pop an element off a heap.
   *  @param  first  Start of heap.
   *  @param  last   End of heap.
   *  @ingroup heap
   *
   *  This operation pops the top of the heap.  The elements first and last-1
   *  are swapped and [first,last-1) is made into a heap.
  */
  template<typename _RandomAccessIterator>
    inline void
    pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
    {
      typedef typename iterator_traits<_RandomAccessIterator>::value_type _ValueType;

      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)
      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)

      std::__pop_heap(__first, __last - 1, __last - 1, _ValueType(*(__last - 1)));
    }

  template<typename _RandomAccessIterator, typename _Distance,
	   typename _Tp, typename _Compare>
    void
    __adjust_heap(_RandomAccessIterator __first, _Distance __holeIndex,
		  _Distance __len, _Tp __value, _Compare __comp)
    {
      _Distance __topIndex = __holeIndex;
      _Distance __secondChild = 2 * __holeIndex + 2;
      while (__secondChild < __len) {
	if (__comp(*(__first + __secondChild), *(__first + (__secondChild - 1))))
	  __secondChild--;
	*(__first + __holeIndex) = *(__first + __secondChild);
	__holeIndex = __secondChild;
	__secondChild = 2 * (__secondChild + 1);
      }
      if (__secondChild == __len) {
	*(__first + __holeIndex) = *(__first + (__secondChild - 1));
	__holeIndex = __secondChild - 1;
      }
      std::__push_heap(__first, __holeIndex, __topIndex, __value, __comp);
    }

  template<typename _RandomAccessIterator, typename _Tp, typename _Compare>
    inline void 
    __pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
	       _RandomAccessIterator __result, _Tp __value, _Compare __comp)
    {
      typedef typename iterator_traits<_RandomAccessIterator>::difference_type _Distance;
      *__result = *__first;
      std::__adjust_heap(__first, _Distance(0), _Distance(__last - __first), 
			 __value, __comp);
    }

  /**
   *  @brief  Pop an element off a heap using comparison functor.
   *  @param  first  Start of heap.
   *  @param  last   End of heap.
   *  @param  comp   Comparison functor to use.
   *  @ingroup heap
   *
   *  This operation pops the top of the heap.  The elements first and last-1
   *  are swapped and [first,last-1) is made into a heap.  Comparisons are
   *  made using comp.
  */
  template<typename _RandomAccessIterator, typename _Compare>
    inline void 
    pop_heap(_RandomAccessIterator __first,
	     _RandomAccessIterator __last, _Compare __comp)
    {
      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)

      typedef typename iterator_traits<_RandomAccessIterator>::value_type _ValueType;
      std::__pop_heap(__first, __last - 1, __last - 1, _ValueType(*(__last - 1)), __comp);
    }

  /**
   *  @brief  Construct a heap over a range.
   *  @param  first  Start of heap.
   *  @param  last   End of heap.
   *  @ingroup heap
   *
   *  This operation makes the elements in [first,last) into a heap.
  */
  template<typename _RandomAccessIterator>
    void 
    make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
    {
      typedef typename iterator_traits<_RandomAccessIterator>::value_type
	  _ValueType;
      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
	  _DistanceType;

      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)
      __glibcxx_function_requires(_LessThanComparableConcept<_ValueType>)

      if (__last - __first < 2) return;
      _DistanceType __len = __last - __first;
      _DistanceType __parent = (__len - 2)/2;
	
      while (true) {
	std::__adjust_heap(__first, __parent, __len, _ValueType(*(__first + __parent)));
	if (__parent == 0) return;
	__parent--;
      }
    }

  /**
   *  @brief  Construct a heap over a range using comparison functor.
   *  @param  first  Start of heap.
   *  @param  last   End of heap.
   *  @param  comp   Comparison functor to use.
   *  @ingroup heap
   *
   *  This operation makes the elements in [first,last) into a heap.
   *  Comparisons are made using comp.
  */
  template<typename _RandomAccessIterator, typename _Compare>
    inline void 
    make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
	      _Compare __comp)
    {
      typedef typename iterator_traits<_RandomAccessIterator>::value_type
	  _ValueType;
      typedef typename iterator_traits<_RandomAccessIterator>::difference_type
	  _DistanceType;

      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)

      if (__last - __first < 2) return;
      _DistanceType __len = __last - __first;
      _DistanceType __parent = (__len - 2)/2;
	
      while (true) {
	std::__adjust_heap(__first, __parent, __len,
			   _ValueType(*(__first + __parent)), __comp);
	if (__parent == 0) return;
	__parent--;
      }
    }

  /**
   *  @brief  Sort a heap.
   *  @param  first  Start of heap.
   *  @param  last   End of heap.
   *  @ingroup heap
   *
   *  This operation sorts the valid heap in the range [first,last).
  */
  template<typename _RandomAccessIterator>
    void
    sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
    {
      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)
      __glibcxx_function_requires(_LessThanComparableConcept<
	    typename iterator_traits<_RandomAccessIterator>::value_type>)

      while (__last - __first > 1)
	std::pop_heap(__first, __last--);
    }

  /**
   *  @brief  Sort a heap using comparison functor.
   *  @param  first  Start of heap.
   *  @param  last   End of heap.
   *  @param  comp   Comparison functor to use.
   *  @ingroup heap
   *
   *  This operation sorts the valid heap in the range [first,last).
   *  Comparisons are made using comp.
  */
  template<typename _RandomAccessIterator, typename _Compare>
    void 
    sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
	      _Compare __comp)
    {
      // concept requirements
      __glibcxx_function_requires(_Mutable_RandomAccessIteratorConcept<
	    _RandomAccessIterator>)

      while (__last - __first > 1)
	std::pop_heap(__first, __last--, __comp);
    }

} // namespace std

#endif /* _STL_HEAP_H */

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