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priorityq-heap.h
1 /*
2 ** Author: Eric Veach, July 1994.
3 **
4 */
5 
6 #ifndef __priorityq_heap_h_
7 #define __priorityq_heap_h_
8 
9 /* Use #define's so that another heap implementation can use this one */
10 
11 #define PQkey PQHeapKey
12 #define PQhandle PQHeapHandle
13 #define PriorityQ PriorityQHeap
14 
15 #define pqNewPriorityQ(leq) __gl_pqHeapNewPriorityQ(leq)
16 #define pqDeletePriorityQ(pq) __gl_pqHeapDeletePriorityQ(pq)
17 
18 /* The basic operations are insertion of a new key (pqInsert),
19  * and examination/extraction of a key whose value is minimum
20  * (pqMinimum/pqExtractMin). Deletion is also allowed (pqDelete);
21  * for this purpose pqInsert returns a "handle" which is supplied
22  * as the argument.
23  *
24  * An initial heap may be created efficiently by calling pqInsert
25  * repeatedly, then calling pqInit. In any case pqInit must be called
26  * before any operations other than pqInsert are used.
27  *
28  * If the heap is empty, pqMinimum/pqExtractMin will return a NULL key.
29  * This may also be tested with pqIsEmpty.
30  */
31 #define pqInit(pq) __gl_pqHeapInit(pq)
32 #define pqInsert(pq, key) __gl_pqHeapInsert(pq, key)
33 #define pqMinimum(pq) __gl_pqHeapMinimum(pq)
34 #define pqExtractMin(pq) __gl_pqHeapExtractMin(pq)
35 #define pqDelete(pq, handle) __gl_pqHeapDelete(pq, handle)
36 #define pqIsEmpty(pq) __gl_pqHeapIsEmpty(pq)
37 
38 /* Since we support deletion the data structure is a little more
39  * complicated than an ordinary heap. "nodes" is the heap itself;
40  * active nodes are stored in the range 1..pq->size. When the
41  * heap exceeds its allocated size (pq->max), its size doubles.
42  * The children of node i are nodes 2i and 2i+1.
43  *
44  * Each node stores an index into an array "handles". Each handle
45  * stores a key, plus a pointer back to the node which currently
46  * represents that key (ie. nodes[handles[i].node].handle == i).
47  */
48 
49 typedef void *PQkey;
50 typedef long PQhandle;
51 typedef struct PriorityQ PriorityQ;
52 
53 typedef struct
54 {
55  PQhandle handle;
56 } PQnode;
57 typedef struct
58 {
59  PQkey key;
60  PQhandle node;
61 } PQhandleElem;
62 
63 struct PriorityQ
64 {
65  PQnode *nodes;
66  PQhandleElem *handles;
67  long size, max;
68  PQhandle freeList;
69  int initialized;
70  int (*leq)(PQkey key1, PQkey key2);
71 };
72 
73 PriorityQ *pqNewPriorityQ(int (*leq)(PQkey key1, PQkey key2));
74 void pqDeletePriorityQ(PriorityQ *pq);
75 
76 void pqInit(PriorityQ *pq);
77 PQhandle pqInsert(PriorityQ *pq, PQkey key);
78 PQkey pqExtractMin(PriorityQ *pq);
79 void pqDelete(PriorityQ *pq, PQhandle handle);
80 
81 #define __gl_pqHeapMinimum(pq) ((pq)->handles[(pq)->nodes[1].handle].key)
82 #define __gl_pqHeapIsEmpty(pq) ((pq)->size == 0)
83 
84 #endif
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