1. Linked Lists

2. Array List Issues
Painful insert/remove at start/middle

3. Array List Issues Painful insert/remove at start/middle
Average ~n/2 wasted space
Worse if shrinks

4. Array List Issues Painful insert/remove at start/middle
Average ~n/2 wasted space
Worse if shrinks
Data kept in a single block
Memory fragmentation may prevent grow():
array other data

5. Linked List
Linked List : Implement List ADT with linked series of nodes
One value per node
Pointer to next node

6. Linked List Implementation will change performance
Space always based on current size of list
But extra required for pointers
Data distributed in lots of little pieces + no worries about allocating big blocks - cache coherence
BigO's will change

7. Linked List List Node: Stores one item of data
Stores a pointer to another node

8. Linked List Linked ListNodes:
Each node starts with nullptr for next value

9. Linked List Linked ListNodes:
Each node starts with nullptr for next value
Set next to address of other node to form a chain
End of chain points to null

10. Linked List
Goal : List ADT implemented with LinkNodes What does list need to keep track of?
Bare minimum: Where first node is

11. Traversal
Traverse Linked Lists with pointer
Start at head

12. Traversal Traverse Linked Lists with pointer Start at head
Advance by following next

13. Traversal Traverse Linked Lists with pointer Start at head
Advance by following next

14. Traversal Traverse Linked Lists with pointer Start at head
Advance by following next
Stop when you hit null

15. Putting It Together
Print each item:

16. listSize int listSize() If size not stored…
Find by traversing and counting:
int listSize()
count = 0
current = head
while current is not null
count++
current = current->next return count

17. Partial Traversal Which node is at index 2?
How do we retrieve the value?

18. Partial Traversal Which node is at index 2?
How do we retrieve the value?
Start from head (0) Advance to next twice Return data

19. Partial Traversal retrieveAt(num)
Start from head (0) Advance to next num times Print what is there

20. Partial Traversal retrieveAt(num)
Start from head (0) Advance to next num times If hit nullptr, error Print what is there
currentnext on nullptr will blow up

21. Remove Start
How do we remove the first node?

22. Remove Start Bad attempt 1: head  head->next node1 is now garbage
need to delete but no pointer!

23. Remove Start
Bad attempt 2: delete head
Lost track of node 2

24. Remove Start Can't delete node1 unless we store link first
RemoveFirst() if head == nullptr error Node* temp = head->next delete head head = temp

25. Remove Start Can't delete node1 unless we store link first
RemoveFirst() if head == nullptr error Node* temp = head->next delete head head = temp

26. Remove Start Can't delete node1 unless we store link first
RemoveFirst() if head == nullptr error Node* temp = head->next delete head head = temp

27. Insert Start
Now we want to add 12 to start of list…

28. Insert Start Now we want to add 12 to start of list
Need a new Node
InsertFirst(12) Node* temp = new Node(12)

29. Insert Start Now we want to add 12 to start of list
new node will point to old head
InsertFirst(12) Node* temp = new Node(12) temp->next = head

30. Insert Start Now we want to add 12 to start of list
head can then point to temp
InsertFirst(12) Node* temp = new Node(12) temp->next = head head = temp

31. Insert At
Want to insert a new value at index 2

32. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value)

33. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value) Node* temp = head

34. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value) Node* temp = head Advance to next 2 times

35. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value) Node* temp = head Advance to next 2 times TOO FAR No way to adjust node2's pointer!

36. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value) Node* temp = head Advance to next 1 times

37. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value) Node* temp = head Advance to next 1 times newNode->next = temp->next

38. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value) Node* temp = head Advance to next 1 times newNode->next = temp->next temp->next = newNode

39. Insert At Want to insert a new value at index 2 InsertAt(index, value)
Node* newNode = new Node(value) Node* temp = head Advance to next (index – 1) times newNode->next = temp->next temp->next = newNode What special case still won't work?

40. Insert At Want to insert a new value at index InsertAt(index, value)
If index = InsertFirst(value) Else Node* newNode = new Node(value) Node* temp = head Advance to next (index – 1) times If temp == nullptr error newNode->next = temp->next temp->next = newNode