1. Traversing a Linked List
Linked Lists
Introduction
Building a Linked List
Traversing a Linked List
Deleting a Node
Dr. Hyrum D. Carroll
(with some material from Dale & Weems’s Programming and Problem Solving with C++ slides)

2. Declarations for a Dynamic Linked List
// Type declarations
struct NodeType {
char info;
NodeType* link; };
// Variable DECLARATIONS
NodeType* head;
NodeType* ptr;
. info link
‘A’ x600

3. ptr is a pointer to a node
. info link
‘A’ x600
ptr

4. *ptr is the entire node pointed to by ptr
‘A’ 0x600
. info link
*ptr

5. ptr->info is a node member
. info link
‘A’ 0x600
ptr->info or
(*ptr).info // Equivalent

6. ptr->link is a node member
. info link
‘A’ 0x600
ptr->link or
(*ptr).link // Equivalent

7. Pointer Dereferencing and Member Selection
ptr
. info link
‘A’ x600
ptr
ptr
. info link
‘A’ x600
*ptr
ptr
. info link
(*ptr).info or
ptr->info
‘A’ x600

8. Building a Linked List

9. Building a Linked List newNodePtr head newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

10. Building a Linked List newNodePtr 0x200 head
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

11. Building a Linked List newNodePtr 0x200 head ‘L’
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

12. Building a Linked List newNodePtr 0x200 head ‘L’ NULL
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

13. Building a Linked List newNodePtr 0x200 head ‘L’ NULL
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

14. Building a Linked List newNodePtr 0x500 0x200 head ‘L’ NULL
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

15. Building a Linked List newNodePtr 0x500 0x200 head ‘I’ ‘L’ NULL
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

16. Building a Linked List newNodePtr 0x500 0x200 head ‘I’ 0x200 ‘L’ NULL
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

17. Building a Linked List newNodePtr 0x500 0x200 head ‘I’ 0x200 ‘L’ NULL
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

18. Building a Linked List ‘I’ 0x200 ‘L’ NULL newNodePtr 0x300 0x500 0x200
head
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

19. Building a Linked List ‘T’ ‘I’ 0x200 ‘L’ NULL newNodePtr
0x x x200
head
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

20. Building a Linked List ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL newNodePtr
0x x x200
head
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

21. Building a Linked List ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL newNodePtr
0x x x200
head
newNodePtr = new NodeType;
newNodePtr->info = ‘L’;
newNodePtr->link = NULL;
head = newNodePtr;
newNodePtr->info = ‘I’;
newNodePtr->link = head;
newNodePtr->info = ‘T’;

22. Traversing a Linked List

23. Traversing a Linked List
ptr
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

24. Traversing a Linked List
ptr
0x300
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

25. Traversing a Linked List
ptr
0x300
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

26. Traversing a Linked List
ptr
0x300
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘T’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

27. Traversing a Linked List
ptr
0x500
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output:
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

28. Traversing a Linked List
ptr
0x500
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output:
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

29. Traversing a Linked List
ptr
0x500
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘I’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

30. Traversing a Linked List
ptr
0x200
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘I’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

31. Traversing a Linked List
ptr
0x200
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘I’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

32. Traversing a Linked List
ptr
0x200
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘L’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

33. Traversing a Linked List
ptr
NULL
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘L’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

34. Traversing a Linked List
ptr
NULL
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘L’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

35. Traversing a Linked List
ptr
NULL
‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
Output: ‘L’
ptr = head;
while (ptr != NULL){
cout << ptr->info;
ptr = ptr->link; }

36. Deleting a Node

37. Deleting Node ’I’ prev curr ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

38. Deleting Node ’I’ prev curr NULL 0x300 ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

39. Deleting Node ’I’ prev curr NULL 0x300 ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

40. Deleting Node ’I’ prev curr 0x300 0x300 ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

41. Deleting Node ’I’ prev curr 0x300 0x300 ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

42. Deleting Node ’I’ prev curr 0x300 0x300 ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

43. Deleting Node ’I’ prev curr 0x300 0x300 ‘T’ 0x500 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

44. Deleting Node ’I’ prev curr 0x300 0x300 ‘T’ 0x200 ‘I’ 0x200 ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

45. Deleting Node ’I’ prev curr 0x300 0x300 ‘T’ 0x200 ? ? ‘L’ NULL
0x x x200
head
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

46. Deleting Node ’I’ prev curr 0x300 NULL 0x300 0x200 head
‘T’ 0x ‘L’ NULL
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

47. Deleting Node ’I’ prev curr 0x300 NULL 0x300 0x200 head
‘T’ 0x ‘L’ NULL
0x300
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer

48. Deleting Node ’I’ prev curr 0x300 NULL ‘T’ 0x200 ‘L’ NULL 0x300 0x200
head
0x x ‘L’ NULL
// find node ’I’
NodeType *curr = head, *prev = NULL;
while( curr != NULL && curr->info != ’I’){
prev = curr;
curr = curr->link; }
if( curr == NULL){/*’I’ not found*/ return; }
prev->link = curr->link; // copy pointer to prev’s
delete curr; // free up memory on the heap
curr = NULL; // clean up the pointer