priorityqueuelinked.c

#include <stdio.h>
#include <stdlib.h>

struct node { 
    int data; 
    struct node *next; 
};
struct node *front = NULL;

// In this implementation, the higher value = higher priority. 
// It inserts items in descending sorted order.
void enqueuePriority(int value) {
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = value;
    
    // If list is empty or new node has highest priority, put it at front
    if (front == NULL || value > front->data) {
        newNode->next = front;
        front = newNode;
        return;
    }
    
    // Otherwise, traverse to find its proper sorted spot
    struct node *temp = front;
    while (temp->next != NULL && temp->next->data >= value) {
        temp = temp->next;
    }
    newNode->next = temp->next;
    temp->next = newNode;
}

void dequeue() {
    if (front == NULL) {
        printf("Priority Queue is Empty\n");
        return;
    }
    struct node *temp = front;
    printf("Processed highest priority item: %d\n", front->data);
    front = front->next;
    free(temp);
}

void display() {
    struct node *temp = front;
    if (temp == NULL) { printf("Priority Queue is Empty\n"); return; }
    printf("Priority Queue: ");
    while (temp != NULL) { 
        printf("%d -> ", temp->data); 
        temp = temp->next; 
    }
    printf("NULL\n");
}

int main() {
    enqueuePriority(10); enqueuePriority(30); enqueuePriority(20);
    display(); 
    dequeue(); 
    display();
    return 0;
}