#include <stdio.h>
#include <stdlib.h>
typedef struct {
int key;
} element;
struct queue {
element data;
struct queue* link;
};
typedef struct queue* queueptr;
queueptr front = NULL;
queueptr rear = NULL;
void insert(element item) {
queueptr temp;
temp = (queueptr)malloc(sizeof(struct queue));
temp->data = item;
temp->link = NULL;
if (rear)
rear->link = temp;
else
front = temp;
rear = temp;
}
element delete() {
queueptr temp;
element item;
if (front) {
temp = front;
item = front->data;
front = front->link;
if (front == NULL)
rear = NULL;
free(temp);
} else {
item.key = -1;
}
return item;
}
void display() {
queueptr temp = front;
if (temp == NULL) {
printf("Queue empty\n");
return;
}
while (temp) {
printf("%d\t", temp->data.key);
temp = temp->link;
}
printf("\n");
}
int main(void) {
int choice;
element item;
while (1) {
printf("Enter\n 1. Insert\n 2. Delete\n 3. Display\n 4. Exit\n");
scanf("%d", &choice);
switch (choice) {
case 1:
printf("Enter data to be inserted: ");
scanf("%d", &item.key);
insert(item);
break;
case 2:
item = delete();
if (item.key == -1)
printf("Queue empty\n");
else
printf("Element deleted: %d\n", item.key);
break;
case 3:
display();
break;
case 4:
exit(0);
default:
printf("Invalid choice\n");
}
}
return 0;
}