數據結構之樹和遞歸算法

今天,我們來討論樹的部分算法和實現以及如何使用遞歸算法.

好了,我們看如何實現的吧.我還是要重申一遍,大家寫程序的時候,一定要注意思想,方法,風格這三方面.因爲,當你維護一個大型系統的時候,你會發現,它會減輕你好多負擔的.

代碼如下:

#ifndef _TREE_H_
#define _TREE_H_

typedef void* HTREEITEM;

template <typename T>
class CTree;
template <typename T>
struct Elem
{
 friend class CTree<T>;
 private:
  T   elem;
  Elem<T> * plChild;
  Elem<T> * prChild;

 public:
  Elem():plChild(NULL),prChild(NULL){};
  Elem( T e ):plChild(NULL),prChild(NULL),elem(e){};
};

template <typename T>
class CTree
{
 private:
  Elem<T> * m_pRoot;

 public:
  CTree( const T e );
  virtual ~CTree();

  HTREEITEM InsertItem( const T e, HTREEITEM hParent = NULL );

  void PreOrder( HTREEITEM hStartItem = NULL );
  void InOrder( HTREEITEM hStartItem = NULL );
  void PostOrder( HTREEITEM hStartItem = NULL );
};

template <typename T>
CTree<T>::CTree( const T e )
{
 m_pRoot = new Elem<T>(e);
}

template <typename T>
CTree<T>::~CTree()
{
 if ( m_pRoot )
 {
  if ( m_pRoot->plChild )
  {
   delete m_pRoot->plChild;
  }
  if ( m_pRoot->prChild )
  {
   delete m_pRoot->prChild;
  }
  delete m_pRoot;
 }
}

template <typename T>
HTREEITEM CTree<T>::InsertItem( const T e, HTREEITEM hParent/* = NULL*/ )
{
 Elem<T> * pParent = NULL;
 Elem<T> * pElem  = NULL;

 pElem = new Elem<T>(e);
 if ( hParent == NULL )
  pParent = m_pRoot;
 else
  pParent = static_cast<Elem<T>*>(hParent);
 
 if ( pParent ->plChild == NULL )
 {
  pParent ->plChild = pElem;
 }
 else
 {
  pParent = pParent ->plChild;
  while( pParent ->prChild )
  { 
   pParent = pParent ->prChild ;
  }
  pParent ->prChild = pElem;
 }
 
 return static_cast<HTREEITEM>(pElem);
}

template <typename T>
void CTree<T>::PreOrder( HTREEITEM hStartItem/* == NULL*/ )
{
 Elem<T> * pStart = NULL;

 if ( hStartItem == NULL )
  pStart = m_pRoot;
 else
  pStart = static_cast<Elem<T>*>(hStartItem);
 
 if ( pStart )
 {
  cout << pStart ->elem ;
  if ( pStart ->plChild )
  {
   PreOrder( static_cast<HTREEITEM>(pStart ->plChild) );
  }
  if ( pStart ->prChild )
  {
   PreOrder( static_cast<HTREEITEM>(pStart ->prChild) );
  }
 }
}

template <typename T>
void CTree<T>::InOrder( HTREEITEM hStartItem /* = NULL  */ )
{
 Elem<T> * pStart = NULL;
 
 if ( hStartItem == NULL )
  pStart = m_pRoot;
 else
  pStart = static_cast<Elem<T>*>(hStartItem);
 
 if ( pStart )
 {
  if ( pStart ->plChild )
  {
   PreOrder( static_cast<HTREEITEM>(pStart ->plChild) );
  }
  cout << pStart ->elem ;
  if ( pStart ->prChild )
  {
   PreOrder( static_cast<HTREEITEM>(pStart ->prChild) );
  }
 }
}

template <typename T>
void CTree<T>::PostOrder( HTREEITEM hStartItem /* = NULL  */ )
{
 Elem<T> * pStart = NULL;
 
 if ( hStartItem == NULL )
  pStart = m_pRoot;
 else
  pStart = static_cast<Elem<T>*>(hStartItem);
 
 if ( pStart )
 {
  if ( pStart ->plChild )
  {
   PreOrder( static_cast<HTREEITEM>(pStart ->plChild) );
  }
  if ( pStart ->prChild )
  {
   PreOrder( static_cast<HTREEITEM>(pStart ->prChild) );
  }
  cout << pStart ->elem ;
 }
}

#endif//_TREE_H_ 

至少,我認爲這個代碼是很酷的.呵呵