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ESc101: Fundamentals of Com utin

2011-12-Monsoon Semester

Lecture #29, October 17, 2011

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Announcements

Last date for course drop is 20 th October. I will sign drop requests till 19 th October.

Friday Lab Sections: Lab 9 will be conducted on 18 th (Tuesday) Monday Lab Sections: Lab 10 will not be today, but next week Tuesday Lab Sections: Lab 10 will not be tomorrow may be on 23 rd.

Lab exam in the week of 14 th to 18 th November

Lec-29

La s 11 an 12 wi not e pre-announce to give you practice End-sem exam is on 25 th November, 8:00 AM

Copies can be seen on 28 th afternoon.

1Dheeraj Sanghi, CSE Dept., IIT KanpurESc101, 2011-12-Monsoon

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Recap

Linked lists Deletion at the end Searching for a node Deletion in the middle Insertion in a sorted list

Lec-29 2Dheeraj Sanghi, CSE Dept., IIT KanpurESc101, 2011-12-Monsoon

Recap: Insertion in a sorted list

struct node * insert_mid (struct node * list, int number){

, ,new = ( struct node *) malloc (sizeof (struct node)); // Allocate spacenew->info = number; // Store the information

if (list == NULL) // special case of empty list{ new->next = list;

return new;

if (list->info > number) // special case of new node first{ new->next = list;

return new;}

Lec-29 Dheeraj Sanghi, CSE Dept., IIT KanpurESc101, 2011-12-Monsoon

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Doubly Linked List


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Complex Self-referential structures

A hierarchical structure of nodes where each node can have

pointers to two nodes each node being called a child

struct node {int key;

*struct node *right;

};


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Binary Tree


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Family Tree (Lab 10 assignment)

struct person p;struct familynode *father;struct familynode *mother;struct familynode *spouse;struct familynode *sibling;struct familynode *child;

};


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Family Tree


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Family Tree

name the parents name the spouse name ALL siblings name ALL children


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Stack

- - Example: A stack of books

you can only put books on top, or take out a book from thetop

trying to take out a book from the middle or put a book inthe middle may cause all books to topple

Push: Insert at the beginning Pop: Delete from the beginning


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Stack

Can be easily implemented using regular (single pointer)

linked list. Push

same as inserting a node at the beginning of the linked list code given in lecture # 27

Pop same as deleting a node from the beginning of the linked list

code given in lecture #27


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Queue

- - Example: queue at the railway reservation counter

you can only enter the queue at the end only the person at the head of the queue can leave the queue

(hopefully, after getting the reservation)

Operations: nqueue: nsert at t e en Dequeue: Delete from the beginning


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Queue

Can be easily implemented using regular (single pointer)

linked list. Enqueue

same as inserting a node at the end of the linked list code given in lecture # 27

Dequeue same as deleting a node from the beginning of the linked list

code given in lecture #27


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Queue

Note that either end of the linked list could have been called

only thing that we need to do is to be consistent with thisdefinition in dequeue and enqueue

So the alternate implementation of queue operations will be: Enqueue

same as inserting node at the beginning of the linked list o e g ven n ec ure

Dequeue same as deleting a node at the end of the linked list Code given in lecture #28


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Queue

one operation is done in a single step the other operation requires traversal of the entire list

Can we do both operations in single step? Yes, using doubly linked lists


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Doubly Linked List

struct nodeint key;struct node *prev;

struct node *next;};

s ruc no e ea = ;struct node *tail = NULL;


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Creating the first node

struct node *s

s = (struct node *) malloc (sizeof (struct node));s->key = ;s->prev = NULL;s->prev = NULL;

head = s;tail = s;


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Inserting after a given node

Will not change head May change tail, if the given node ( n ) is the last node e e new no e e s

s->prev = n;s->next = n->next;if (n->next == NULL)

tail = s;else

n->next->prev = s;n->next = s;


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Removing a node

if n-> rev == NULL head = n->next;

elsen->prev->next = n->next;

if (n->next == NULL)tail = n->prev;

e sen->next->prev = n->prev;

free (n);


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Any Questions?

Lec-29 25Dheeraj Sanghi, CSE Dept., IIT KanpurESc101, 2011-12-Monsoon

esc101-lec29

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