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pq.h
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/* The MIT License
Copyright (c) 2023 by Sam H
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
#ifndef LIBPQH
#define LIBPQH
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#define PQ_SIZE 4095 // todo: make this dynamic
#define PQ_PARENT(x) x == 1 ? -1 : (x >> 1)
#define PQ_LEFT(x) x << 1
#define PQ_INIT(type) \
typedef struct type##PriorityQueue { \
type elems[PQ_SIZE]; \
size_t n; \
} type##PriorityQueue; \
\
static inline bool type##PriorityQueueCompare(type *a, type *b); \
\
type##PriorityQueue *type##PriorityQueueCreate() { \
type##PriorityQueue *pq = \
(type##PriorityQueue *)malloc(sizeof(type##PriorityQueue)); \
if (!pq) \
return pq; \
pq->n = 0; \
memset(pq->elems, 0, sizeof(*pq->elems)); \
return pq; \
} \
\
void type##PriorityQueueDestroy(type##PriorityQueue *pq) { \
pq->n = 0; \
free(pq); \
} \
\
static void type##PriorityQueueSwap__(type##PriorityQueue *pq, size_t a, \
size_t b) { \
type tmp = pq->elems[a]; \
pq->elems[a] = pq->elems[b]; \
pq->elems[b] = tmp; \
} \
\
void type##PriorityQueueBubbleUp__(type##PriorityQueue *pq, size_t pos) { \
size_t parent = PQ_PARENT(pos); \
if (parent == -1) { \
return; \
} \
/* Todo: generic compare */ \
if (type##PriorityQueueCompare(&pq->elems[parent], &pq->elems[pos])) { \
type##PriorityQueueSwap__(pq, pos, parent); \
type##PriorityQueueBubbleUp__(pq, parent); \
} \
} \
\
void type##PriorityQueueBubbleDown__(type##PriorityQueue *pq, size_t pos) { \
size_t child, i, minIdx; \
child = PQ_LEFT(pos); \
minIdx = pos; \
\
for (i = 0; i < 2; i++) { \
if ((child + i) <= pq->n) { \
/* Todo: generic compare */ \
if (type##PriorityQueueCompare(&pq->elems[minIdx], \
&pq->elems[child + i])) { \
minIdx = child + i; \
} \
} \
} \
\
if (minIdx != pos) { \
type##PriorityQueueSwap__(pq, pos, minIdx); \
type##PriorityQueueBubbleDown__(pq, minIdx); \
} \
} \
size_t type##PriorityQueueSize(type##PriorityQueue *pq) { return pq->n; } \
\
int type##PriorityQueueInsert(type##PriorityQueue *pq, type elem) { \
if (pq->n >= PQ_SIZE) \
return -1; \
pq->n++; \
size_t i = pq->n; \
pq->elems[i] = elem; \
type##PriorityQueueBubbleUp__(pq, i); \
return 0; \
} \
\
type type##PriorityQueuePop(type##PriorityQueue *pq) { \
if (!pq->n) \
return pq->elems[0]; \
type top = pq->elems[1]; \
pq->elems[1] = pq->elems[pq->n]; \
pq->n--; \
type##PriorityQueueBubbleDown__(pq, 1); \
return top; \
} \
\
type type##PriorityQueueTop(type##PriorityQueue *pq) { \
return pq->elems[pq->n ? 1 : 0]; \
} \
type##PriorityQueue *type##PriorityQueueFrom(type *arr, size_t count) { \
type##PriorityQueue *pq = type##PriorityQueueCreate(); \
if (!pq) \
return pq; \
/*count is truncated if more than PQ_SIZE*/ \
count = count % PQ_SIZE; \
size_t i = 0; \
pq->n = count; \
for (; i < count; i++) \
pq->elems[i + 1] = arr[i]; \
for (i = pq->n >> 1; i >= 1; i--) \
type##PriorityQueueBubbleDown__(pq, i); \
return pq; \
}
#endif /* LIBPQH */