2012-09-11 14:56:36 +00:00
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/*
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* Functions for a rudimentary fast min-heap implementation.
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* Derived from Python's _heapqmodule.c by way of drastic simplification
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* and a few optimizations.
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*/
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/*
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* Original Python _heapqmodule.c implementation was derived directly
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* from heapq.py in Py2.3 which was written by Kevin O'Connor, augmented
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* by Tim Peters, annotated by François Pinard, and converted to C by
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* Raymond Hettinger.
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*/
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#include <stdio.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/types.h>
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#include <stdint.h>
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#include <heapq.h>
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#ifndef NDEBUG
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#define ERROR_CHK
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#endif
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void
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reset_heap(heap_t *heap, __TYPE tot)
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{
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if (heap) {
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heap->len = 0;
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heap->tot = tot;
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}
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}
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static int
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_siftdownmax(heap_t *h, __TYPE startpos, __TYPE pos)
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{
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__TYPE newitem, parent;
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__TYPE parentpos, *heap;
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#ifdef ERROR_CHK
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if (pos >= h->len) {
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fprintf(stderr, "_siftdownmax: index out of range\n");
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return -1;
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}
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#endif
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heap = h->ary;
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newitem = heap[pos];
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/* Follow the path to the root, moving parents down until finding
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a place newitem fits. */
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while (pos > startpos){
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parentpos = (pos - 1) >> 1;
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parent = heap[parentpos];
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if (parent < newitem)
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break;
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heap[pos] = parent;
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pos = parentpos;
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}
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heap[pos] = newitem;
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return 0;
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}
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static int
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_siftupmax(heap_t *h, __TYPE spos, __TYPE epos)
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{
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__TYPE endpos, childpos, rightpos;
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__TYPE newitem, *heap, pos;
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endpos = h->len;
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heap = h->ary;
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#ifdef ERROR_CHK
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2012-12-28 16:42:38 +00:00
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if (spos >= endpos) {
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fprintf(stderr, "_siftupmax: index out of range: %u, len: %u\n", spos, endpos);
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2012-09-11 14:56:36 +00:00
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return -1;
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}
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#endif
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do {
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pos = spos;
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/* Bubble up the smaller child until hitting a leaf. */
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newitem = heap[pos];
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childpos = (pos << 1) + 1; /* leftmost child position */
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while (childpos < endpos) {
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/* Set childpos to index of smaller child. */
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rightpos = childpos + 1;
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if (rightpos < endpos) {
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if (heap[rightpos] < heap[childpos])
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childpos = rightpos;
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}
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/* Move the smaller child up. */
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heap[pos] = heap[childpos];
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pos = childpos;
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childpos = (pos << 1) + 1;
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}
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/* The leaf at pos is empty now. Put newitem there, and and bubble
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it up to its final resting place (by sifting its parents down). */
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heap[pos] = newitem;
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#ifdef ERROR_CHK
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if (_siftdownmax(h, spos, pos) == -1)
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return (-1);
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#else
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_siftdownmax(h, spos, pos);
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#endif
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spos--;
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} while (spos >= epos);
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return (0);
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}
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static int
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_siftupmax_s(heap_t *h, __TYPE spos)
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{
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__TYPE endpos, childpos, rightpos;
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__TYPE newitem, *heap, pos;
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endpos = h->len;
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heap = h->ary;
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#ifdef ERROR_CHK
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2012-12-28 16:42:38 +00:00
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if (spos >= endpos) {
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fprintf(stderr, "_siftupmax: index out of range: %u, len: %u\n", spos, endpos);
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2012-09-11 14:56:36 +00:00
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return -1;
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}
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#endif
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pos = spos;
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/* Bubble up the smaller child until hitting a leaf. */
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newitem = heap[pos];
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childpos = (pos << 1) + 1; /* leftmost child position */
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while (childpos < endpos) {
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/* Set childpos to index of smaller child. */
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rightpos = childpos + 1;
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if (rightpos < endpos) {
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2012-09-11 16:29:08 +00:00
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if (heap[rightpos] < heap[childpos])
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2012-09-11 14:56:36 +00:00
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childpos = rightpos;
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}
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/* Move the smaller child up. */
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heap[pos] = heap[childpos];
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pos = childpos;
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childpos = (pos << 1) + 1;
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}
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/* The leaf at pos is empty now. Put newitem there, and and bubble
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it up to its final resting place (by sifting its parents down). */
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heap[pos] = newitem;
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return (_siftdownmax(h, spos, pos));
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}
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int
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ksmallest(__TYPE *ary, __TYPE len, heap_t *heap)
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{
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__TYPE elem, los;
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__TYPE i, *hp, n;
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n = heap->tot;
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heap->ary = ary;
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hp = ary;
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heap->len = n;
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#ifdef ERROR_CHK
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if(_siftupmax(heap, n/2-1, 0) == -1)
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return (-1);
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#else
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_siftupmax(heap, n/2-1, 0);
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#endif
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los = hp[0];
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for (i = n; i < len; i++) {
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elem = ary[i];
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if (elem >= los) {
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continue;
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}
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hp[0] = elem;
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#ifdef ERROR_CHK
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if (_siftupmax_s(heap, 0) == -1)
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return (-1);
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#else
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_siftupmax_s(heap, 0);
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#endif
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los = hp[0];
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}
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return 0;
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}
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