binarysearchtree.h

《数据结构、算法与应用》从C++语言应用角度列举了要点

// linked binary tree implementation of a binary search tree
// implements all dictionary and bsTree methods

#ifndef binarySearchTree_
#define binarySearchTree_



#include "bsTree.h"
#include "linkedBinaryTree.h"

using namespace std;

template<class K, class E>
class binarySearchTree : public bsTree<K,E>,
                         public linkedBinaryTree<pair<const K, E> >
{
   public:
      // methods of dictionary
      bool empty() const {return treeSize == 0;}
      int size() const {return treeSize;}
      pair<const K, E>* find(const K& theKey) const;
      void insert(const pair<const K, E>& thePair);
      void erase(const K& theKey);

      // additional method of bsTree
      void ascend() {inOrderOutput();}
};

template<class K, class E>
pair<const K, E>* binarySearchTree<K,E>::find(const K& theKey) const
{// Return pointer to matching pair.
 // Return NULL if no matching pair.
   // p starts at the root and moves through
   // the tree looking for an element with key theKey
   binaryTreeNode<pair<const K, E> > *p = root;
   while (p != NULL)
      // examine p->element
      if (theKey < p->element.first)
         p = p->leftChild;
      else
         if (theKey > p->element.first)
            p = p->rightChild;
         else // found matching pair
            return &p->element;

   // no matching pair
   return NULL;
}

template<class K, class E>
void binarySearchTree<K,E>::insert(const pair<const K, E>& thePair)
{// Insert thePair into the tree. Overwrite existing
 // pair, if any, with same key.
   // find place to insert
   binaryTreeNode<pair<const K, E> > *p = root,
                                     *pp = NULL;
   while (p != NULL)
   {// examine p->element
      pp = p;
      // move p to a child
      if (thePair.first < p->element.first)
         p = p->leftChild;
      else
         if (thePair.first > p->element.first)
            p = p->rightChild;
         else
         {// replace old value
            p->element.second = thePair.second;
            return;
         }
   }

   // get a node for thePair and attach to pp
   binaryTreeNode<pair<const K, E> > *newNode
                 = new binaryTreeNode<pair<const K, E> > (thePair);
   if (root != NULL) // the tree is not empty
      if (thePair.first < pp->element.first)
         pp->leftChild = newNode;
      else
         pp->rightChild = newNode;
   else
      root = newNode; // insertion into empty tree
   treeSize++;
}

template<class K, class E>
void binarySearchTree<K,E>::erase(const K& theKey)
{// Delete the pair, if any, whose key equals theKey.

   // search for node with key theKey
   binaryTreeNode<pair<const K, E> > *p = root,
                                     *pp = NULL;
   while (p != NULL && p->element.first != theKey)
   {// move to a child of p
      pp = p;
      if (theKey < p->element.first)
         p = p->leftChild;
      else
         p = p->rightChild;
   }
   if (p == NULL)
      return; // no pair with key theKey

   // restructure tree
   // handle case when p has two children
   if (p->leftChild != NULL && p->rightChild != NULL)
   {// two children
      // convert to zero or one child case
      // find largest element in left subtree of p
      binaryTreeNode<pair<const K, E> > *s = p->leftChild,
                                       *ps = p;  // parent of s
      while (s->rightChild != NULL)
      {// move to larger element
         ps = s;
         s = s->rightChild;
      }

      // move largest from s to p, can't do a simple move
      // p->element = s->element as key is const
      binaryTreeNode<pair<const K, E> > *q =
         new binaryTreeNode<pair<const K, E> >
             (s->element, p->leftChild, p->rightChild);
      if (pp == NULL)
         root = q;
      else if (p == pp->leftChild)
              pp->leftChild = q;
           else
              pp->rightChild = q;
      if (ps == p) pp = q;
      else pp = ps;
      delete p;
      p = s;
   }

   // p has at most one child
   // save child pointer in c
   binaryTreeNode<pair<const K, E> > *c;
   if (p->leftChild != NULL)
      c = p->leftChild;
   else
      c = p->rightChild;

   // delete p
   if (p == root)
      root = c;
   else
   {// is p left or right child of pp?
      if (p == pp->leftChild)
         pp->leftChild = c;
      else pp->rightChild = c;
   }
   treeSize--;
   delete p;
}

// overload << for pair
template <class K, class E>
ostream& operator<<(ostream& out, const pair<K, E>& x)
   {out << x.first << ' ' << x.second; return out;}
#endif