Mastering Algorithms with C

Name

pqueue_init

Synopsis

void pqueue_init(PQueue *pqueue, int (*compare)(const void *key1, 
   const void *key2), void (*destroy)(void *data));

Return Value

None.

Description

Initializes the priority queue specified by pqueue. This operation must be called for a priority queue before it can be used with any other operation. The compare argument is a function used by various priority queue operations in maintaining the priority queue’s heap property. This function should return 1 if key1 > key2, if key1 = key2, and -1 if key1 < key2 for a priority queue in which large keys have a higher priority. For a priority queue in which smaller keys have a higher priority, compare should reverse the cases that return 1 and -1. The destroy argument provides a way to free dynamically allocated data when pqueue_destroy is called. For example, if the priority queue contains data dynamically allocated using malloc, destroy should be set to free to free the data as the priority queue is destroyed. For structured data containing several dynamically allocated members, destroy should be set to a user-defined function that calls free for each dynamically allocated member as well as for the structure itself. For a priority queue containing data that should not be freed, destroy should be set to NULL.

Complexity

O (1)