340 lines
7.3 KiB
COBOL
340 lines
7.3 KiB
COBOL
// This may look like C code, but it is really -*- C++ -*-
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/*
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Copyright (C) 1988 Free Software Foundation
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written by Dirk Grunwald (grunwald@cs.uiuc.edu)
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adapted for libg++ by Doug Lea (dl@rocky.oswego.edu)
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This file is part of the GNU C++ Library. This library is free
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software; you can redistribute it and/or modify it under the terms of
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the GNU Library General Public License as published by the Free
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Software Foundation; either version 2 of the License, or (at your
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option) any later version. This library is distributed in the hope
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that it will be useful, but WITHOUT ANY WARRANTY; without even the
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implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the GNU Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free Software
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Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifdef __GNUG__
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#pragma implementation
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#endif
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#include <limits.h>
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#include "<T>.PHPQ.h"
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//
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// This defines a Pairing Heap structure
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//
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// See ``The Pairing Heap: A New Form of Self-Adjusting Heap''
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// Fredman, Segdewick et al,
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// Algorithmica (1986) 1:111-129
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//
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// In particular, this implements the pairing heap using the circular
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// list.
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//
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//
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<T>PHPQ::<T>PHPQ(int sz)
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{
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storage = 0;
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root = 0;
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count = 0;
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size = 0;
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prealloc(sz);
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}
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<T>PHPQ::<T>PHPQ(<T>PHPQ& a)
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{
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storage = 0;
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root = 0;
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count = 0;
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size = 0;
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prealloc(a.size);
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for (Pix i = a.first(); i != 0; a.next(i)) enq(a(i));
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}
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void <T>PHPQ::prealloc(int newsize)
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{
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++newsize; // leave a spot for freelist
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if (size != 0)
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{
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int news = size;
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while (news <= newsize) news = (news * 3) / 2;
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newsize = news;
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}
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// see if indices are OK
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<T>PHPQNode test;
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test.sibling = 0;
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test.sibling = ~test.sibling;
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if ((unsigned long)newsize > (unsigned long)(test.sibling))
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error("storage size exceeds index range");
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if (storage == 0)
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{
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storage = new <T>PHPQNode[size = newsize];
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for (int i = 0; i < size; ++i)
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{
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storage[i].sibling = i + 1;
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storage[i].valid = 0;
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}
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storage[size-1].sibling = 0;
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}
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else
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{
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<T>PHPQNode* newstor = new <T>PHPQNode[newsize];
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for (int i = 1; i < size; ++i)
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newstor[i] = storage[i];
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delete [] storage;
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storage = newstor;
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for (int i = size; i < newsize; ++i)
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{
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storage[i].sibling = i + 1;
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storage[i].valid = 0;
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}
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storage[newsize-1].sibling = 0;
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storage[0].sibling = size;
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size = newsize;
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}
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}
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void <T>PHPQ::clear()
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{
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for (int i = 0; i < size; ++i)
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{
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storage[i].sibling = i + 1;
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storage[i].valid = 0;
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}
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storage[size-1].sibling = 0;
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root = 0;
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count = 0;
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}
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Pix <T>PHPQ::enq(<T&> item)
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{
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++count;
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if (storage[0].sibling == 0)
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prealloc(count);
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int cell = storage[0].sibling;
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storage[0].sibling = storage[cell].sibling;
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storage[cell].sibling = 0;
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storage[cell].children = 0;
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storage[cell].item = item;
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storage[cell].valid = 1;
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if (root == 0)
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{
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root = cell;
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return Pix(root);
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}
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else
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{
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int parent;
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int child;
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if (<T>LE(storage[root].item, storage[cell].item))
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{
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parent = root; child = cell;
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}
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else
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{
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parent = cell; child = root;
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}
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int popsKid = storage[parent].children;
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if (popsKid == 0)
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{
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storage[parent].children = child;
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storage[child].sibling = child;
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}
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else
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{
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int temp = storage[popsKid].sibling;
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storage[popsKid].sibling = child;
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storage[child].sibling = temp;
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storage[parent].children = child;
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}
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root = parent;
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return Pix(cell);
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}
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}
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//
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// Item removal is the most complicated routine.
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//
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// We remove the root (should there be one) and then select a new
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// root. The siblings of the root are in a circular list. We continue
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// to pair elements in this list until there is a single element.
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// This element will be the new root.
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void <T>PHPQ::del_front()
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{
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int valid = 0;
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do
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{
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if (root == 0) return;
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if ((valid = storage[root].valid))
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--count;
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storage[root].valid = 0;
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int child = storage[root].children;
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storage[root].sibling = storage[0].sibling;
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storage[0].sibling = root;
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if (child == 0)
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{
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root = 0;
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return;
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}
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else
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{
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while(storage[child].sibling != child)
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{
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// We have at least two kids, but we may only have
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// two kids. So, oneChild != child, but it is possible
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// that twoChild == child.
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int oneChild = storage[child].sibling;
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int twoChild = storage[oneChild].sibling;
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// Remove the two from the sibling list
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storage[child].sibling = storage[twoChild].sibling;
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storage[oneChild].sibling = 0;
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storage[twoChild].sibling = 0;
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int bestChild;
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int worstChild;
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if (<T>LE(storage[oneChild].item, storage[twoChild].item))
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{
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bestChild = oneChild; worstChild = twoChild;
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}
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else
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{
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bestChild = twoChild; worstChild = oneChild;
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}
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int popsKid = storage[bestChild].children;
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if (popsKid == 0)
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{
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storage[bestChild].children = worstChild;
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storage[worstChild].sibling = worstChild;
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}
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else
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{
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int temp = storage[popsKid].sibling;
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storage[popsKid].sibling = worstChild;
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storage[worstChild].sibling = temp;
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storage[bestChild].children = worstChild;
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}
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if (twoChild == child)
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{
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// We have reduced the two to one, so we'll be exiting.
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child = bestChild;
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storage[child].sibling = child;
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}
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else
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{
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// We've removed two siblings, now we need to insert
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// the better of the two
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storage[bestChild].sibling = storage[child].sibling;
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storage[child].sibling = bestChild;
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child = storage[bestChild].sibling;
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}
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}
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root = child;
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}
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} while ( !valid );
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}
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void <T>PHPQ::del(Pix p)
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{
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if (p == 0) error("null Pix");
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int i = int(p);
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if (storage[i].valid)
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{
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if (i == root)
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del_front();
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else
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{
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storage[i].valid = 0;
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--count;
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}
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}
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}
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Pix <T>PHPQ::seek(<T&> key)
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{
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for (int i = 1; i < size; ++i)
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if (storage[i].valid && <T>EQ(storage[i].item, key))
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return Pix(i);
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return 0;
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}
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Pix <T>PHPQ::first()
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{
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for (int i = 1; i < size; ++i)
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if (storage[i].valid)
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return Pix(i);
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return 0;
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}
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void <T>PHPQ::next(Pix& p)
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{
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if (p == 0) return;
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for (int i = int(p)+1; i < size; ++i)
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if (storage[i].valid)
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{
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p = Pix(i);
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return;
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}
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p = 0;
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}
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int <T>PHPQ::OK()
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{
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int v = storage != 0;
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int n = 0;
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for (int i = 0; i < size; ++i) if (storage[i].valid) ++n;
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v &= n == count;
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v &= check_sibling_list(root);
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int ct = INT_MAX;
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n = 0;
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int f = storage[0].sibling;
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while (f != 0 && ct-- > 0)
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{
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f = storage[f].sibling;
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++n;
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}
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v &= ct > 0;
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v &= n <= size - count;
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if (!v) error("invariant failure");
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return v;
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}
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int <T>PHPQ::check_sibling_list(int t)
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{
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if (t != 0)
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{
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int s = t;
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long ct = LONG_MAX; // Lots of chances to find self!
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do
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{
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if (storage[s].valid && !check_sibling_list(storage[s].children))
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return 0;
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s = storage[s].sibling;
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} while (ct-- > 0 && s != t && s != 0);
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if (ct <= 0) return 0;
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}
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return 1;
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}
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