// 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 GNU CC. GNU CC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY. No author or distributor accepts responsibility to anyone for the consequences of using it or for whether it serves any particular purpose or works at all, unless he says so in writing. Refer to the GNU CC General Public License for full details. Everyone is granted permission to copy, modify and redistribute GNU CC, but only under the conditions described in the GNU CC General Public License. A copy of this license is supposed to have been given to you along with GNU CC so you can know your rights and responsibilities. It should be in a file named COPYING. Among other things, the copyright notice and this notice must be preserved on all copies. */ #ifdef __GNUG__ #pragma implementation #endif #include #include ".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. // // PHPQ::PHPQ(int sz) { storage = 0; root = 0; count = 0; size = 0; prealloc(sz); } PHPQ::PHPQ(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 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 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 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 { PHPQNode* newstor = new PHPQNode[newsize]; for (int i = 1; i < size; ++i) newstor[i] = storage[i]; delete [size] 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 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 PHPQ::enq( 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 (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 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 (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 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 PHPQ::seek( key) { for (int i = 1; i < size; ++i) if (storage[i].valid && EQ(storage[i].item, key)) return Pix(i); return 0; } Pix PHPQ::first() { for (int i = 1; i < size; ++i) if (storage[i].valid) return Pix(i); return 0; } void 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 PHPQ::OK() { int v = storage != 0; int n = check_sibling_list(root, 0); v &= n == count; 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 PHPQ::check_sibling_list(int t, int cnt) { if (t != 0) { int s = t; long ct = MAXLONG; // Lots of chances to find self! do { if (storage[s].valid) cnt++; cnt += check_sibling_list(storage[s].children, cnt); s = storage[s].sibling; } while (ct-- > 0 && s != t && s != 0); if (ct <= 0) return -1; } return cnt; }