pq.c

/*
 * In this file, you will write the structures and functions needed to
 * implement a priority queue.  Feel free to implement any helper functions
 * you need in this file to implement a priority queue.  Make sure to add your
 * name and @oregonstate.edu email address below:
 *
 * Name:
 * Email:
 */

#include <stdlib.h>

#include "pq.h"

/*
 * This is the structure that represents a priority queue.  You must define
 * this struct to contain the data needed to implement a priority queue.
 * in addition, you want to define an element struct with both data and priority, 
 * corresponding to the elements of the priority queue. 
 */
struct pq;


/*
 * This function should allocate and initialize an empty priority queue and
 * return a pointer to it.
 */
struct pq* pq_create() {
  return NULL;
}


/*
 * This function should free the memory allocated to a given priority queue.
 * Note that this function SHOULD NOT free the individual elements stored in
 * the priority queue.  That is the responsibility of the caller.
 *
 * Params:
 *   pq - the priority queue to be destroyed.  May not be NULL.
 */
void pq_free(struct pq* pq) {

}


/*
 * This function should return 1 if the specified priority queue is empty and
 * 0 otherwise.
 *
 * Params:
 *   pq - the priority queue whose emptiness is to be checked.  May not be
 *     NULL.
 *
 * Return:
 *   Should return 1 if pq is empty and 0 otherwise.
 */
int pq_isempty(struct pq* pq) {
  return 1;
}


/*
 * This function should insert a given element into a priority queue with a
 * specified priority value.  Note that in this implementation, higher priority
 * values are given precedent, and higher place in the queue.  In other words, the
 * element in the priority queue with the highest priority value should be the
 * FIRST one returned.
 *
 * Params:
 *   pq - the priority queue into which to insert an element.  May not be
 *     NULL.
 *   data - the data value to be inserted into pq.
 *   priority - the priority value to be assigned to the newly-inserted
 *     element.  Note that in this implementation, higher priority values
 *     should correspond to the first elements.  In other words,
 *     the element in the priority queue with the highest priority value should
 *     be the FIRST one returned.
 */
void pq_insert(struct pq* pq, void* data, int priority) {

}


/*
 * This function should return the data of the first element in a priority
 * queue, i.e. the data associated with the element with highest priority value.
 *
 * Params:
 *   pq - the priority queue from which to fetch a value.  May not be NULL or
 *     empty.
 *
 * Return:
 *   Should return the data of the first item in pq, i.e. the item with
 *   max priority value.
 */
void* pq_max(struct pq* pq) {
  return NULL;
}


/*
 * This function should return the priority value of the first item in a
 * priority queue, i.e. the item with highest priority value.
 *
 * Params:
 *   pq - the priority queue from which to fetch a priority value.  May not be
 *     NULL or empty.
 *
 * Return:
 *   Should return the priority value of the first item in pq, i.e. the item
 *   with highest priority value.
 */
int pq_max_priority(struct pq* pq) {
  return 0;
}


/*
 * This function should return the value of the first item in a priority
 * queue, i.e. the item with highest priority value, and then remove that item
 * from the queue.
 *
 * Params:
 *   pq - the priority queue from which to remove a value.  May not be NULL or
 *     empty.
 *
 * Return:
 *   Should return the value of the first item in pq, i.e. the item with
 *   highest priority value.
 */
void* pq_max_dequeue(struct pq* pq) {
  return NULL;
}