stl_heap.h

/*
 *
 * 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.
 */

/* NOTE: This is an internal header file, included by other STL headers.
 *   You should not attempt to use it directly.
 */

#ifndef __SGI_STL_INTERNAL_HEAP_H
#define __SGI_STL_INTERNAL_HEAP_H

__STL_BEGIN_NAMESPACE

#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma set woff 1209
#endif

// Heap-manipulation functions: push_heap, pop_heap, make_heap, sort_heap.
// heap的操作函数push_heap，pop_heap，make_heap，sort_heap
template <class _RandomAccessIterator, class _Distance, class _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;
}

template <class _RandomAccessIterator, class _Distance, class _Tp>
inline void 
__push_heap_aux(_RandomAccessIterator __first,
                _RandomAccessIterator __last, _Distance*, _Tp*)
{ //新值必须置于底部容器的最尾端，此即第一个洞号（last - first）- 1
  __push_heap(__first, _Distance((__last - __first) - 1), _Distance(0), 
              _Tp(*(__last - 1)));
}

template <class _RandomAccessIterator>
inline void 
push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
{ //这个函数被调用时，新元素已经被置于底部容器的最尾端了
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  __STL_REQUIRES(typename iterator_traits<_RandomAccessIterator>::value_type,
                 _LessThanComparable);
  __push_heap_aux(__first, __last,
                  __DISTANCE_TYPE(__first), __VALUE_TYPE(__first));
}

template <class _RandomAccessIterator, class _Distance, class _Tp, 
          class _Compare>
void
__push_heap(_RandomAccessIterator __first, _Distance __holeIndex,
            _Distance __topIndex, _Tp __value, _Compare __comp)
{ //这个push_heap函数不允许指定大小比较标准
  _Distance __parent = (__holeIndex - 1) / 2;   //找出父节点
  while (__holeIndex > __topIndex && __comp(*(__first + __parent), __value)) { //当未到达顶端，切父节点小于新值（于是不符合heap的次序特性）
    *(__first + __holeIndex) = *(__first + __parent); //令洞值的父节点
    __holeIndex = __parent;                           //调整洞号，向上提升至父节点（percolate up）
    __parent = (__holeIndex - 1) / 2;                 //新洞的父节点
  }                                                   //持续至顶端，或满足heap的次序特性为止
  *(__first + __holeIndex) = __value;                 //令洞值为新值，完成插入操作
}

template <class _RandomAccessIterator, class _Compare,
          class _Distance, class _Tp>
inline void 
__push_heap_aux(_RandomAccessIterator __first,
                _RandomAccessIterator __last, _Compare __comp,
                _Distance*, _Tp*) 
{
  __push_heap(__first, _Distance((__last - __first) - 1), _Distance(0), 
              _Tp(*(__last - 1)), __comp);
}

template <class _RandomAccessIterator, class _Compare>
inline void 
push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
          _Compare __comp)
{
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  __push_heap_aux(__first, __last, __comp,
                  __DISTANCE_TYPE(__first), __VALUE_TYPE(__first));
}

template <class _RandomAccessIterator, class _Distance, class _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;
  }
  __push_heap(__first, __holeIndex, __topIndex, __value);
}

template <class _RandomAccessIterator, class _Tp, class _Distance>
inline void 
__pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
           _RandomAccessIterator __result, _Tp __value, _Distance*)
{
  *__result = *__first;
  __adjust_heap(__first, _Distance(0), _Distance(__last - __first), __value);
}

template <class _RandomAccessIterator, class _Tp>
inline void 
__pop_heap_aux(_RandomAccessIterator __first, _RandomAccessIterator __last,
               _Tp*)
{
  __pop_heap(__first, __last - 1, __last - 1, 
             _Tp(*(__last - 1)), __DISTANCE_TYPE(__first));
}

template <class _RandomAccessIterator>
inline void pop_heap(_RandomAccessIterator __first, 
                     _RandomAccessIterator __last)
{
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  __STL_REQUIRES(typename iterator_traits<_RandomAccessIterator>::value_type,
                 _LessThanComparable);
  __pop_heap_aux(__first, __last, __VALUE_TYPE(__first));
}

template <class _RandomAccessIterator, class _Distance,
          class _Tp, class _Compare>
void
__adjust_heap(_RandomAccessIterator __first, _Distance __holeIndex,
              _Distance __len, _Tp __value, _Compare __comp)
{
  _Distance __topIndex = __holeIndex;
  _Distance __secondChild = 2 * __holeIndex + 2;  //洞节点的右子节点
  while (__secondChild < __len) {                 //比较洞节点的左右两个子值，然后以secondChild代表较大子节点
    if (__comp(*(__first + __secondChild), *(__first + (__secondChild - 1))))
      __secondChild--; //percolate down (下朔)，令较大值为洞值，再令洞下移至较大节点处
    *(__first + __holeIndex) = *(__first + __secondChild);
    __holeIndex = __secondChild;                  //找出新洞节点的右子节点
    __secondChild = 2 * (__secondChild + 1);
  }
  if (__secondChild == __len) {                   //没有右子节点，只有左子节点
    *(__first + __holeIndex) = *(__first + (__secondChild - 1)); // 令左子节点的值为洞值，再令洞号下移至左子节点处
    __holeIndex = __secondChild - 1;
  }// 这样确实不行
  __push_heap(__first, __holeIndex, __topIndex, __value, __comp);
}

template <class _RandomAccessIterator, class _Tp, class _Compare, 
          class _Distance>
inline void 
__pop_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
           _RandomAccessIterator __result, _Tp __value, _Compare __comp,
           _Distance*)
{
  *__result = *__first;     //设定尾值为首值，即尾值即为欲求的结果，可由客户端稍后再以底层容器的pop_back取出尾值
  __adjust_heap(__first, _Distance(0), _Distance(__last - __first), 
                __value, __comp); //重新调整heap，洞号为0（完全二叉树的根），欲调整值为value（原尾值）
}

template <class _RandomAccessIterator, class _Tp, class _Compare>
inline void 
__pop_heap_aux(_RandomAccessIterator __first,
               _RandomAccessIterator __last, _Tp*, _Compare __comp)
{ //pop的结果应是底部容器的第一个元素，首先设定与调整值为尾部，然后将首值调至尾节点，然后重调[first, last-1)，使之重新成一个合格的heap
  __pop_heap(__first, __last - 1, __last - 1, _Tp(*(__last - 1)), __comp,
             __DISTANCE_TYPE(__first));
}

template <class _RandomAccessIterator, class _Compare>
inline void 
pop_heap(_RandomAccessIterator __first,
         _RandomAccessIterator __last, _Compare __comp)
{
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  __pop_heap_aux(__first, __last, __VALUE_TYPE(__first), __comp);
}

template <class _RandomAccessIterator, class _Tp, class _Distance>
void 
__make_heap(_RandomAccessIterator __first,
            _RandomAccessIterator __last, _Tp*, _Distance*)
{
  if (__last - __first < 2) return;
  _Distance __len = __last - __first;
  _Distance __parent = (__len - 2)/2;
    
  while (true) {
    __adjust_heap(__first, __parent, __len, _Tp(*(__first + __parent)));
    if (__parent == 0) return;
    __parent--;
  }
}

template <class _RandomAccessIterator>
inline void 
make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
{
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  __STL_REQUIRES(typename iterator_traits<_RandomAccessIterator>::value_type,
                 _LessThanComparable);
  __make_heap(__first, __last,
              __VALUE_TYPE(__first), __DISTANCE_TYPE(__first));
}

template <class _RandomAccessIterator, class _Compare,
          class _Tp, class _Distance>
void
__make_heap(_RandomAccessIterator __first, _RandomAccessIterator __last,
            _Compare __comp, _Tp*, _Distance*)
{
  if (__last - __first < 2) return;     //如果长度是0或1，不必重新排列
  _Distance __len = __last - __first;   //找出第一个需重排的子树头部，以parent标示出，由于任何节点都不需要执行perlocate down
  _Distance __parent = (__len - 2)/2;   //所以有一下计算，parent命名不佳，名为holeIndex更好
    
  while (true) {                        //重排以parent为首的子树，len是为了让__adjust_heap函数判断操作范围
    __adjust_heap(__first, __parent, __len, _Tp(*(__first + __parent)),
                  __comp);
    if (__parent == 0) return;          //走完根节点就结束
    __parent--;                         //（已重排的子树的）头部向前一个节点
  }
}

template <class _RandomAccessIterator, class _Compare>
inline void 
make_heap(_RandomAccessIterator __first, 
          _RandomAccessIterator __last, _Compare __comp)
{   //make_heap将[first, last)排序为一个heap
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  __make_heap(__first, __last, __comp,
              __VALUE_TYPE(__first), __DISTANCE_TYPE(__first));
}

template <class _RandomAccessIterator>
void sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
{    //这个sort_heap不允许指定大小比较标准
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  __STL_REQUIRES(typename iterator_traits<_RandomAccessIterator>::value_type,
                 _LessThanComparable);//每执行一次pop_heap函数，极值（在STL heap中为极大值）被放在尾端
  while (__last - __first > 1)        //扣除尾端再执行一次pop_heap函数（），次极值又被放在新尾端，一直下去，最后就为排序结果    
    pop_heap(__first, __last--);      //每执行pop_heap()一次，操作范围即退缩一格；得到的结果是从小到达的结果
}

template <class _RandomAccessIterator, class _Compare>
void 
sort_heap(_RandomAccessIterator __first,
          _RandomAccessIterator __last, _Compare __comp)
{
  __STL_REQUIRES(_RandomAccessIterator, _Mutable_RandomAccessIterator);
  while (__last - __first > 1)
    pop_heap(__first, __last--, __comp);
}

#if defined(__sgi) && !defined(__GNUC__) && (_MIPS_SIM != _MIPS_SIM_ABI32)
#pragma reset woff 1209
#endif

__STL_END_NAMESPACE

#endif /* __SGI_STL_INTERNAL_HEAP_H */

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