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#include "priority_queue.h"
#include <stdlib.h>
PriorityQueue *initialize() {
PriorityQueue *queue = malloc(sizeof(PriorityQueue));
queue->size = 0;
queue->head = NULL;
return queue;
}
static Node *create_node(int priority, int data) {
Node *node = malloc(sizeof(Node));
node->priority = priority;
node->data = data;
node->next = NULL;
return node;
}
// This function is constant time O(1)
int size(PriorityQueue *queue) {
return queue->size;
}
static int compare(const int x, const int y) {
return x == y ? 0 : x > y ? 1 : -1;
}
void enqueue(Node *self, int priority, int data) {
if (self->next == NULL) {
self->next = create_node(priority, data);
return;
}
int comparison = compare(self->next->priority, priority);
if (comparison == 0) {
return enqueue(self->next, priority, data);
}
if (comparison < 0) {
return enqueue(self->next, priority, data);
}
self->next = create_node(priority, data);
}
// This function is linear time O(n)
void add(PriorityQueue *queue, int priority, int data) {
queue->size++;
if (!queue->head) {
queue->head = create_node(priority, data);
return;
}
if (compare(queue->head->priority, priority) <= 0)
return enqueue(queue->head, priority, data);
Node *node = create_node(priority, data);
node->next = queue->head;
queue->head = node;
}
// This function is constant time O(1)
int delete_min(PriorityQueue *queue) {
if (queue->head) {
Node *tmp = queue->head;
int data = tmp->data;
queue->head = tmp->next;
queue->size--;
free(tmp);
return data;
}
return 0;
}
void destroy(PriorityQueue *queue) {
Node *current = queue->head;
Node *tmp;
while(current) {
tmp = current, current = current->next;
if (tmp) free(tmp);
}
free(queue);
}
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