PairNode<Etype> *
PairHeap<Etype>::CombineSiblings( PairNode<Etype> *FirstSibling )
{
if( FirstSibling->NextSibling == NULL )
return FirstSibling;
// Allocate the array
Vector<PairNode<Etype> *> TreeArray( CurrentSize );
// Store the subtrees in an array
int NumSiblings;
for( NumSiblings = 0; FirstSibling != NULL; NumSiblings++ )
{
TreeArray[ NumSiblings ] = FirstSibling;
FirstSibling->Prev->NextSibling = NULL; // break links
FirstSibling = FirstSibling->NextSibling;
}
TreeArray[ NumSiblings ] = NULL;
// Combine the subtrees two at a time, going left to right
int i;
for( i = 0; i+1 < NumSiblings; i+=2 )
CompareAndLink( TreeArray[ i ], TreeArray[ i + 1 ] );
int j = i - 2;
// j has the result of the last CompareAndLink.
// If an odd number of trees, get the last one
if( j == NumSiblings - 3 )
CompareAndLink( TreeArray[ j ], TreeArray[ j + 2 ] );
// Now go right to left, merging last tree with
// next to last. The result becomes the new last.
for( ; j >= 2; j -= 2 )
CompareAndLink( TreeArray[ j - 2 ], TreeArray[ j ] );
PairNode<Etype> *Result = TreeArray[ 0 ];
return Result;
}
PairHeap
CombineSiblings( Position FirstSibling )
{
static Position TreeArray[ MaxSiblings ];
int i, j, NumSiblings;
/* If only one tree, return it */
if( FirstSibling->NextSibling == NULL )
return FirstSibling;
/* Place each subtree in TreeArray */
for( NumSiblings = 0; FirstSibling != NULL; NumSiblings++ )
{
TreeArray[ NumSiblings ] = FirstSibling;
FirstSibling->Prev->NextSibling = NULL; /* Break links */
FirstSibling = FirstSibling->NextSibling;
}
TreeArray[ NumSiblings ] = NULL;
/* Combine the subtrees two at a time, */
/* going left to right */
for( i = 0; i + 1 < NumSiblings; i += 2 )
TreeArray[ i ] = CompareAndLink(
TreeArray[ i ], TreeArray[ i + 1 ] );
/* j has the result of the last CompareAndLink */
/* If an odd number of trees, get the last one */
j = i - 2;
if( j == NumSiblings - 3 )
TreeArray[ j ] = CompareAndLink(
TreeArray[ j ], TreeArray[ j + 2 ] );
/* Now go right to left, merging last tree with */
/* next to last. The result becomes the new last */
for( ; j >= 2; j -= 2 )
TreeArray[ j - 2 ] = CompareAndLink(
TreeArray[ j - 2 ], TreeArray[ j ] );
return TreeArray[ 0 ];
}
PairNode<Etype> *
PairHeap<Etype>::Insert( const Etype & X )
{
PairNode<Etype> *NewNode = new PairNode<Etype>( X );
CurrentSize++;
if( Root == NULL )
Root = NewNode;
else
CompareAndLink( Root, NewNode );
return NewNode;
}
PairHeap
Insert( ElementType Item, PairHeap H, Position *Loc )
{
Position NewNode;
NewNode = malloc( sizeof( struct PairNode ) );
if( NewNode == NULL )
FatalError( "Out of space!!!" );
NewNode->Element = Item;
NewNode->LeftChild = NewNode->NextSibling = NULL;
NewNode->Prev = NULL;
*Loc = NewNode;
if( H == NULL )
return NewNode;
else
return CompareAndLink( H, NewNode );
}
PairHeap
DecreaseKey( Position P, ElementType Delta, PairHeap H )
{
if( Delta < 0 )
Error( "DecreaseKey called with negative Delta" );
P->Element -= Delta;
if( P == H )
return H;
if( P->NextSibling != NULL )
P->NextSibling->Prev = P->Prev;
if( P->Prev->LeftChild == P )
P->Prev->LeftChild = P->NextSibling;
else
P->Prev->NextSibling = P->NextSibling;
P->NextSibling = NULL;
return CompareAndLink( H, P );
}
void
PairHeap<Etype>::DecreaseKey( PairNode<Etype> *P, const Etype & NewVal )
{
if( P->Element < NewVal )
cerr << "DecreaseKey called with larger value!" << endl;
else
{
P->Element = NewVal;
if( P != Root )
{
if( P->NextSibling != NULL )
P->NextSibling->Prev = P->Prev;
if( P->Prev->LeftChild == P )
P->Prev->LeftChild = P->NextSibling;
else
P->Prev->NextSibling = P->NextSibling;
P->NextSibling = NULL;
CompareAndLink( Root, P );
}
}
}
