Q. Devise a representation for a given list where insertions and deletions can be made at both the ends. Such a structure is called Deque (which means Double ended queue). Write functions for inserting and deleting at both the ends. 

Ans:

struct Deque

{

int info;

struct Deque *left, *right;

}*head, *tail;

add(struct Deque *p, int x)

{

struct Deque *temp;

temp = malloc (sizeof(struct Deque), 1);

temp -> info = x;

if(p == head)

{

temp->right = head; temp->left = NULL; head->left = temp;

head = temp;

}

else if(p == tail)

{

temp->left = tail; temp->right = NULL; tail->right = temp; tail = temp;

}

}

delete(struct Deque *p, int x)

{

struct Deque *temp;

if(p == head)

{

temp = head;

head = head->right;

head->left = NULL; temp->right = NULL; free(temp);

}

else if(p == tail)

{

temp = tail;

tail = tail->left; tail->right = NULL; temp->left = NULL; free(temp);

}

}