C++ Programming Code Examples
C++ > Data Structures and Algorithm Analysis in C++ Code Examples
Implementation for deterministic skip list
/* Implementation for deterministic skip list */
#include "DSL.h"
/**
* Construct the tree.
* inf is the largest Comparable
* and is used to signal failed finds.
*/
template <class Comparable>
DSL<Comparable>::DSL( const Comparable & inf ) : INFINITY( inf )
{
bottom = new SkipNode<Comparable>( );
bottom->right = bottom->down = bottom;
tail = new SkipNode<Comparable>( INFINITY );
tail->right = tail;
header = new SkipNode<Comparable>( INFINITY, tail, bottom );
}
/**
* Copy constructor.
* Left as an exercise.
*/
template <class Comparable>
DSL<Comparable>::DSL( const DSL<Comparable> & rhs ) : INFINITY( rhs.INFINITY)
{
cout << "Copy constructor is unimplemented" << endl;
}
/**
* Destructor.
*/
template <class Comparable>
DSL<Comparable>::~DSL( )
{
makeEmpty( );
delete header;
delete tail;
delete bottom;
}
/**
* Insert item x into the DSL.
*/
template <class Comparable>
void DSL<Comparable>::insert( const Comparable & x )
{
SkipNode<Comparable> *current = header;
bottom->element = x;
while( current != bottom )
{
while( current->element < x )
current = current->right;
// If gap size is 3 or at bottom level and
// must insert, then promote middle element
if( current->down->right->right->element < current->element )
{
current->right = new SkipNode<Comparable>( current->element,
current->right, current->down->right->right );
current->element = current->down->right->element;
}
else
current = current->down;
}
// Raise height of DSL if necessary
if( header->right != tail )
header = new SkipNode<Comparable>( INFINITY, tail, header );
}
/**
* Remove item x from the DSL. Unimplemented.
*/
template <class Comparable>
void DSL<Comparable>::remove( const Comparable & x )
{
cout << "Sorry, remove unimplemented; " << x <<
" still present" << endl;
}
/**
* Find the smallest item in the tree.
* Return smallest item or INFINITY if empty.
*/
template <class Comparable>
const Comparable & DSL<Comparable>::findMin( ) const
{
if( isEmpty( ) )
return INFINITY;
SkipNode<Comparable> *current = header;
while( current->down != bottom )
current = current->down;
return elementAt( current );
}
/**
* Find the largest item in the tree.
* Return the largest item or INFINITY if empty.
*/
template <class Comparable>
const Comparable & DSL<Comparable>::findMax( ) const
{
if( isEmpty( ) )
return INFINITY;
SkipNode<Comparable> *current = header;
for( ; ; )
if( current->right->right != tail )
current = current->right;
else if( current->down != bottom )
current = current->down;
else
return elementAt( current );
}
/**
* Find item x in the tree.
* Return the matching item or INFINITY if not found.
*/
template <class Comparable>
const Comparable & DSL<Comparable>::find( const Comparable & x ) const
{
SkipNode<Comparable> *current = header;
bottom->element = x;
for( ; ; )
if( x < current->element )
current = current->down;
else if( current->element < x )
current = current->right;
else
return elementAt( current );
}
/**
* Make the tree logically empty.
*/
template <class Comparable>
void DSL<Comparable>::makeEmpty( )
{
reclaimMemory( header );
header->right = tail;
header->down = bottom;
}
/**
* Test if the tree is logically empty.
* Return true if empty, false otherwise.
*/
template <class Comparable>
bool DSL<Comparable>::isEmpty( ) const
{
return header->right == tail && header->down == bottom;
}
/**
* Internal method to get element field from node t.
* Return the element field or INFINITY if t is at the bottom.
*/
template <class Comparable>
const Comparable & DSL<Comparable>::
elementAt( SkipNode<Comparable> *t ) const
{
if( t == bottom )
return INFINITY;
else
return t->element;
}
/**
* Print the DSL.
*/
template <class Comparable>
void DSL<Comparable>::printList( ) const
{
SkipNode<Comparable> *current = header;
while( current->down != bottom )
current = current->down;
while( current->right != tail )
{
cout << current->element << endl;
current = current->right;
}
}
/**
* Deep copy. Left as an exercise
*/
template <class Comparable>
const DSL<Comparable> &
DSL<Comparable>::operator=( const DSL<Comparable> & rhs )
{
if( this != &rhs )
cout << "Sorry, operator= is unimplemented" << endl;
return *this;
}
/**
* reclaimMemory is left as an exercise.
* Hint: delete from top level to bottom level.
*/
template <class Comparable>
void DSL<Comparable>::reclaimMemory( SkipNode<Comparable> *t ) const
{
if( t != bottom )
cout << "reclaimMemory is unimplemented -- leaking!" << endl;
}
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