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
Up to n wasted space (if just grew)
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 Memory
+ No extra space for future growth
- Extra required for pointers : 4/8 bytes per node

7. Linked List Implementation will change performance
Memory allocated in lots of pieces + no worries about allocating big blocks - lots of calls to new/delete - poorer cache use

8. Linked List
Implementation will change performance
BigO's will change…

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

10. Linked Nodes Linked ListNodes:
Each node starts with nullptr for next value

11. Linked List Nodes 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

12. Nodes vs Pointers new Node: Creating a new permanent thing
Need a pointer to keep track of it
Need to delete at some point

13. Nodes vs Pointers pointer variable: May point at May need to delete
New memory
Existing memory
May need to delete
Only if “owns” memory

14. Linked List LinkedList : Object that manages linked ListNode chain
Minimal implementation: Where first node is

15. Traversal
Traverse Linked Lists with pointer
Start at head

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

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

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

19. Putting It Together
Print each item:

20. 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

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

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

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

24. 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

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

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

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

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

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

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

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

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

33. 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

34. 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

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

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

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

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 2 times

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 2 times TOO FAR No way to adjust node2's pointer!

40. 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

41. 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

42. 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

43. 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?

44. 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

45. BigO's What is BigO for our basic linked list operations? InsertStart
Insert at middle
InsertEnd
Retrieve First Value
Retrieve Middle Value
Remove From End
Remove From Beginning
Get Length

46. BigO's What is BigO for our basic linked list operations? O(1) O(n)
InsertStart
Insert at middle
InsertEnd
Retrieve First Value
Retrieve Middle Value
Remove From End
Remove From Beginning
Get Length
 O(1)
O(n)
 O(n)
  O(1)
O(n) 
 O(1)