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+// This may look like C code, but it is really -*- C++ -*-
+/*
+Copyright (C) 1988 Free Software Foundation
+ written by Dirk Grunwald (grunwald@cs.uiuc.edu)
+ adapted for libg++ by Doug Lea (dl@rocky.oswego.edu)
+
+This file is part of the GNU C++ Library. This library is free
+software; you can redistribute it and/or modify it under the terms of
+the GNU Library General Public License as published by the Free
+Software Foundation; either version 2 of the License, or (at your
+option) any later version. This library is distributed in the hope
+that it will be useful, but WITHOUT ANY WARRANTY; without even the
+implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+PURPOSE. See the GNU Library General Public License for more details.
+You should have received a copy of the GNU Library General Public
+License along with this library; if not, write to the Free Software
+Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+
+#ifdef __GNUG__
+#pragma implementation
+#endif
+#include <values.h>
+#include "<T>.PHPQ.h"
+
+//
+// This defines a Pairing Heap structure
+//
+// See ``The Pairing Heap: A New Form of Self-Adjusting Heap''
+// Fredman, Segdewick et al,
+// Algorithmica (1986) 1:111-129
+//
+// In particular, this implements the pairing heap using the circular
+// list.
+//
+//
+
+<T>PHPQ::<T>PHPQ(int sz)
+{
+ storage = 0;
+ root = 0;
+ count = 0;
+ size = 0;
+ prealloc(sz);
+}
+
+<T>PHPQ::<T>PHPQ(<T>PHPQ& a)
+{
+ storage = 0;
+ root = 0;
+ count = 0;
+ size = 0;
+ prealloc(a.size);
+ for (Pix i = a.first(); i != 0; a.next(i)) enq(a(i));
+}
+
+
+void <T>PHPQ::prealloc(int newsize)
+{
+ ++newsize; // leave a spot for freelist
+ if (size != 0)
+ {
+ int news = size;
+ while (news <= newsize) news = (news * 3) / 2;
+ newsize = news;
+ }
+ // see if indices are OK
+ <T>PHPQNode test;
+ test.sibling = 0;
+ test.sibling = ~test.sibling;
+ if ((unsigned long)newsize > (unsigned long)(test.sibling))
+ error("storage size exceeds index range");
+
+ if (storage == 0)
+ {
+ storage = new <T>PHPQNode[size = newsize];
+ for (int i = 0; i < size; ++i)
+ {
+ storage[i].sibling = i + 1;
+ storage[i].valid = 0;
+ }
+ storage[size-1].sibling = 0;
+ }
+ else
+ {
+ <T>PHPQNode* newstor = new <T>PHPQNode[newsize];
+ for (int i = 1; i < size; ++i)
+ newstor[i] = storage[i];
+ delete [] storage;
+ storage = newstor;
+ for (i = size; i < newsize; ++i)
+ {
+ storage[i].sibling = i + 1;
+ storage[i].valid = 0;
+ }
+ storage[newsize-1].sibling = 0;
+ storage[0].sibling = size;
+ size = newsize;
+ }
+}
+
+
+void <T>PHPQ::clear()
+{
+ for (int i = 0; i < size; ++i)
+ {
+ storage[i].sibling = i + 1;
+ storage[i].valid = 0;
+ }
+ storage[size-1].sibling = 0;
+ root = 0;
+ count = 0;
+}
+
+Pix <T>PHPQ::enq(<T&> item)
+{
+ ++count;
+ if (storage[0].sibling == 0)
+ prealloc(count);
+
+ int cell = storage[0].sibling;
+ storage[0].sibling = storage[cell].sibling;
+ storage[cell].sibling = 0;
+ storage[cell].children = 0;
+ storage[cell].item = item;
+ storage[cell].valid = 1;
+
+ if (root == 0)
+ {
+ root = cell;
+ return Pix(root);
+ }
+ else
+ {
+ int parent;
+ int child;
+
+ if (<T>LE(storage[root].item, storage[cell].item))
+ {
+ parent = root; child = cell;
+ }
+ else
+ {
+ parent = cell; child = root;
+ }
+ int popsKid = storage[parent].children;
+
+ if (popsKid == 0)
+ {
+ storage[parent].children = child;
+ storage[child].sibling = child;
+ }
+ else
+ {
+ int temp = storage[popsKid].sibling;
+ storage[popsKid].sibling = child;
+ storage[child].sibling = temp;
+ storage[parent].children = child;
+ }
+ root = parent;
+ return Pix(cell);
+ }
+}
+
+//
+// Item removal is the most complicated routine.
+//
+// We remove the root (should there be one) and then select a new
+// root. The siblings of the root are in a circular list. We continue
+// to pair elements in this list until there is a single element.
+// This element will be the new root.
+
+void <T>PHPQ::del_front()
+{
+ int valid = 0;
+ do
+ {
+ if (root == 0) return;
+ if (valid = storage[root].valid)
+ --count;
+ storage[root].valid = 0;
+ int child = storage[root].children;
+ storage[root].sibling = storage[0].sibling;
+ storage[0].sibling = root;
+
+ if (child == 0)
+ {
+ root = 0;
+ return;
+ }
+ else
+ {
+ while(storage[child].sibling != child)
+ {
+ // We have at least two kids, but we may only have
+ // two kids. So, oneChild != child, but it is possible
+ // that twoChild == child.
+
+ int oneChild = storage[child].sibling;
+ int twoChild = storage[oneChild].sibling;
+
+ // Remove the two from the sibling list
+
+ storage[child].sibling = storage[twoChild].sibling;
+ storage[oneChild].sibling = 0;
+ storage[twoChild].sibling = 0;
+
+ int bestChild;
+ int worstChild;
+
+ if (<T>LE(storage[oneChild].item, storage[twoChild].item))
+ {
+ bestChild = oneChild; worstChild = twoChild;
+ }
+ else
+ {
+ bestChild = twoChild; worstChild = oneChild;
+ }
+ int popsKid = storage[bestChild].children;
+
+ if (popsKid == 0)
+ {
+ storage[bestChild].children = worstChild;
+ storage[worstChild].sibling = worstChild;
+ }
+ else
+ {
+ int temp = storage[popsKid].sibling;
+ storage[popsKid].sibling = worstChild;
+ storage[worstChild].sibling = temp;
+ storage[bestChild].children = worstChild;
+ }
+ if (twoChild == child)
+ {
+ // We have reduced the two to one, so we'll be exiting.
+ child = bestChild;
+ storage[child].sibling = child;
+ }
+ else
+ {
+ // We've removed two siblings, now we need to insert
+ // the better of the two
+ storage[bestChild].sibling = storage[child].sibling;
+ storage[child].sibling = bestChild;
+ child = storage[bestChild].sibling;
+ }
+ }
+ root = child;
+ }
+ } while ( !valid );
+}
+
+void <T>PHPQ::del(Pix p)
+{
+ if (p == 0) error("null Pix");
+ int i = int(p);
+ if (storage[i].valid)
+ {
+ if (i == root)
+ del_front();
+ else
+ {
+ storage[i].valid = 0;
+ --count;
+ }
+ }
+}
+
+
+Pix <T>PHPQ::seek(<T&> key)
+{
+ for (int i = 1; i < size; ++i)
+ if (storage[i].valid && <T>EQ(storage[i].item, key))
+ return Pix(i);
+ return 0;
+}
+
+Pix <T>PHPQ::first()
+{
+ for (int i = 1; i < size; ++i)
+ if (storage[i].valid)
+ return Pix(i);
+ return 0;
+}
+
+
+void <T>PHPQ::next(Pix& p)
+{
+ if (p == 0) return;
+ for (int i = int(p)+1; i < size; ++i)
+ if (storage[i].valid)
+ {
+ p = Pix(i);
+ return;
+ }
+ p = 0;
+}
+
+int <T>PHPQ::OK()
+{
+ int v = storage != 0;
+ int n = 0;
+ for (int i = 0; i < size; ++i) if (storage[i].valid) ++n;
+ v &= n == count;
+ v &= check_sibling_list(root);
+ int ct = MAXLONG;
+ n = 0;
+ int f = storage[0].sibling;
+ while (f != 0 && ct-- > 0)
+ {
+ f = storage[f].sibling;
+ ++n;
+ }
+ v &= ct > 0;
+ v &= n <= size - count;
+ if (!v) error("invariant failure");
+ return v;
+}
+
+
+int <T>PHPQ::check_sibling_list(int t)
+{
+ if (t != 0)
+ {
+ int s = t;
+ long ct = MAXLONG; // Lots of chances to find self!
+ do
+ {
+ if (storage[s].valid && !check_sibling_list(storage[s].children))
+ return 0;
+ s = storage[s].sibling;
+ } while (ct-- > 0 && s != t && s != 0);
+ if (ct <= 0) return 0;
+ }
+ return 1;
+}
+
+
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