1. Hassan Khosravi / Geoffrey Tien
Linked Lists
October 06, 2017
Hassan Khosravi / Geoffrey Tien

2. Hassan Khosravi / Geoffrey Tien
Unordered arrays
Arrays are easy to code and to visualise, and offer rapid access to elements using the [] operator
e.g. printf("salary is $%.2f\n", staff[85].salary);
Consider an array with a capacity of 𝑛
Note that capacity may be different from the number of items stored in the array
October 06, 2017
Hassan Khosravi / Geoffrey Tien

3. Hassan Khosravi / Geoffrey Tien
Unordered arrays
What is the time complexity of inserting an item into an array without holes, when order does not matter? 18 9 26 41 12 75 37 60
Insert 15?
What is the time complexity of removing an item into an array without holes, when order does not matter? 18 9 26 41 12 75 37 60
Remove 18?
October 06, 2017
Hassan Khosravi / Geoffrey Tien

4. Hassan Khosravi / Geoffrey Tien
Ordered arrays
What is the time complexity of inserting an item into an array without holes, when order matters? 9 12 18 26 37 41 60 75
Insert 15?
What is the time complexity of removing an item into an array without holes, when order matters? 9 12 18 26 37 41 60 75
Remove 18?
October 06, 2017
Hassan Khosravi / Geoffrey Tien

5. Hassan Khosravi / Geoffrey Tien
Linked list nodes
A linked list is a dynamic data structure that consists of nodes linked together
A node is a data structure that contains
data
the location (address) of the next node
The data portion of a node can contain one or more items or structures
typedef struct node {
int data;
struct node* next;
} node;
typedef struct player {
int jersey_number;
char* name;
struct player* next;
} player;
October 06, 2017
Hassan Khosravi / Geoffrey Tien

6. Hassan Khosravi / Geoffrey Tien
Linked lists
A linked list is a chain of nodes, where each node indicates where in (heap) memory the next item can be found
stack
heap
front 32 76 11 54 32 76 11 54
October 06, 2017
Hassan Khosravi / Geoffrey Tien

7. Modifying linked lists
Inserting an item into a linked list 32 76 54 11 76 22 11 54 32 22
New nodes created using malloc() as needed
Removing an item from a linked list 32 76 22 54 11 32 76 11 54
Removed nodes must be deallocated using free()!
October 06, 2017
Hassan Khosravi / Geoffrey Tien

8. Linked list dis/advantages
Linked list is constructed from nodes in the heap, can be added as needed, and removed at runtime
The size of the list does not need to be "guessed" ahead of time
Disadvantages
To access a particular node (starting from the front of the list), may need to traverse the list to reach – 𝑂 𝑛
Linked list nodes have additional overhead to store pointers
Harder to program, debug, and test
October 06, 2017
Hassan Khosravi / Geoffrey Tien

9. Hassan Khosravi / Geoffrey Tien
Linked list traversal
Traversal through a linked list can be done with a node pointer variable
e.g. to access the 4th element in a list:
// assuming we have node* front
node* ptr = front;
int i;
for (i = 0; i < 4; i++) {
ptr = ptr->next; }
// exited loop, ptr references 4th node
printf("%d", ptr->data);
ptr
front 76 22 11 54 32
October 06, 2017
Hassan Khosravi / Geoffrey Tien

10. Readings for this lesson
Thareja
Chapter 6 (Linked lists)
Algorithm and data structure visualisations
Linked list:
October 06, 2017
Hassan Khosravi / Geoffrey Tien