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_10.QueueUsingLL.c
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_10.QueueUsingLL.c
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#include <stdio.h>
#include<stdlib.h>
struct node
{
int data;
struct node* next;
};
struct node* front = NULL;
struct node* rear = NULL;
struct node* enqueue()
{
struct node* new = (struct node*)malloc(sizeof(struct node));
printf("\nEnter the data to be inserted:");
scanf("%d",&new->data);
if(rear == NULL) //insertion to an empty queue
{
front = new;
rear = new;
return 0 ;
}
rear->next = new;
rear = new;
return 0;
//return rear;
}
struct node* dequeue()
{
if(front == NULL) // empty queue
printf("\n**EMPTY QUEUE**\n");
else
{
struct node* ptr = front;
if(front->next == NULL) //single element in queue
{
front = NULL;
rear = NULL;
free(ptr);
}
else
{
front = front->next;
free(ptr);
}
}
return 0;
//return front;
}
void Display ()
{
if(front == NULL)
{
printf("\n**EMPTY QUEUE**\n");
return ;
}
printf("\nQUEUE ELEMENTS:\n");
for(struct node* i=front; i!=NULL;i=i->next)
{
printf("%d\t",i->data);
}
}
int main()
{
int flag = 0,choice;
printf("\n**IMPLEMENTATION OF QUEUE USING LINKED LISTS**\n");
while(flag==0)
{
printf("\n-----------------------------------------------------\n");
printf("\nEnter your choice:\n\t1.ENQUEUE\n\t2.DEQUEUE\n\t3.Display\n\t4.Exit\nChoice:");
scanf("%d",&choice);
switch(choice)
{
case 1:
{
enqueue();
//rear=enqueue();
break;
}
case 2:
{
dequeue();
//front=dequeue();
break;
}
case 3:
{
Display();
break;
}
case 4:
{
flag=1;
break;
}
default:
{
printf("\nINVALID CHOICE\n");
break;
}
}
}
return 0;
}