C program to implement double ended queue ADT using doubly linked list
by · October 22, 2019
//program to implement double ended queue adt using doubly linked list
#include
#include
/*declaring a structure to create a node*/
struct node
{
int data;
struct node *prev, *next;
};
struct node *head = NULL, *tail = NULL;
struct node * createNode[int data]
{
/*allocating implicit memory to the node*/
struct node *newnode = [struct node *]malloc[sizeof [struct node]];
newnode->data = data;
newnode->next = newnode->prev = NULL;
return [newnode];
}
/* create sentinel[dummy head & tail] that helps us to do insertion and deletion operation at front and rear so easily. And these dummy head and tail wont get deleted till the end of execution of this program */
void createSentinels[] /*creating a head and tail*/ {
head = createNode[0];
tail = createNode[0];
head->next = tail;
tail->prev = head;
}
/* insertion at the front of the queue */
void enqueueAtFront[int data]
{
struct node *newnode, *temp;
newnode = createNode[data];
temp = head->next;
head->next = newnode;
newnode->prev = head;
newnode->next = temp;
temp->prev = newnode;
}
/*insertion at the rear of the queue */
void enqueueAtRear[int data]
{
struct node *newnode, *temp;
newnode = createNode[data];
temp = tail->prev;
tail->prev = newnode;
newnode->next = tail;
newnode->prev = temp;
temp->next = newnode;
}
/* deletion at the front of the queue */
void dequeueAtFront[]
{
struct node *temp;
if [head->next == tail]
{
printf["Queue is empty\n"];
}
else
{
temp = head->next;
head->next = temp->next;
temp->next->prev = head;
free[temp];
}
return;
}
/* deletion at the rear of the queue */
void dequeueAtRear[]
{
struct node *temp;
if [tail->prev == head]
{
printf["Queue is empty\n"];
}
else
{
temp = tail->prev;
tail->prev = temp->prev;
temp->prev->next = tail;
free[temp];
}
return;
}
/* display elements present in the queue */
void display[]
{
struct node *temp;
if [head->next == tail]
{
printf["Queue is empty\n"];
return;
}
temp = head->next;
while [temp != tail]
{
printf["%-3d", temp->data];
temp = temp->next;
}
printf["\n"];
}
/*main program*/
int main[]
{
int data, ch;
createSentinels[];
while [1]
{
printf["1. Enqueue at front\n2. Enqueue at rear\n"];
printf["3. Dequeue at front\n4. Dequeue at rear\n"];
printf["5. Display\n6. Exit\n"];
printf["Enter your choice:"];
scanf["%d", &ch];
switch [ch] /*switch case*/
{
case 1:
printf["Enter the data to insert:"];
scanf["%d", &data];
enqueueAtFront[data];
break;
case 2:
printf["Enter ur data to insert:"];
scanf["%d", &data];
enqueueAtRear[data];
break;
case 3:
dequeueAtFront[];
break;
case 4:
dequeueAtRear[];
break;
case 5:
display[];
break;
case 6:
exit[0];
default:
printf[" enter correct option\n"];
break;
} /*end of switch case*/
}
return 0;
}