1. Linked Lists
Dr. Jose Annunziato

2. The Bank Application
enum TransactionType { DEPOSIT, WITHDRAW }; struct Date { int month, day, year; int hour, minute, second; }; struct Transaction { struct Node { Date date; Transaction* tx; // data TransactionType type; Node* next; string description; } float amount;

3. Linked Lists
head
Node
tx next
tx next
tx next
NULL
Transaction

4. Creating a List By Hand Declaring the pointer:
Transaction* tx1, tx2, tx3;
Node* node1, node2, node3, head;
Creating the data:
tx1 = new Transaction;
(*tx1).amount = ;
tx2 = new Transaction;
(*tx2).amount = ;
tx3 = new Transaction;
(*tx3).amount = ;

5. Creating the List
Node* node1 = new Node; (*node1).next = NULL; (*node1).tx = tx1; Node* node2 = new Node; (*node2).next = node1; (*node2).tx = tx2; Node* node3 = new Node; (*node3).next = node2; (*node3).tx = tx3; head = node3;

6. The -> Notation
Using (*structure).member notation can be cumbersome
Use the equivalent syntax structure->member instead
This Syntax Is Equivalent To:
(*tx1).amount = ; tx->amount = ;
(*tx2).amount = ; tx->amount = ;
(*tx3).amount = ; tx->amount = ;

7. Create List Node* createList ( Transaction* transaction ) {
Node* newNode = new Node;
newNode->next = NULL;
newNode->transaction = transaction;
return newNode; }

8. Push Node
Pushing a node needs to modify the head of the list, therefore we pass the address of an address (**)
void push ( Node** list, Transaction* tx ) {
Node* newNode = new Node;
newNode->next = *list;
newNode->transaction = tx;
*list = newNode; }

9. Traversing a List Follow the next pointer until you reach NULL
void displayList ( Node* list ) {
Node* current = list;
do {
Transaction* tx = current->transaction;
displayTransaction ( *tx );
current = current->next;
} while ( current != NULL ); }

10. Search By Amount Search by traversing a list and comparing each node
Transaction* searchAmount ( Node* list, float amt ) {
Node* current = list;
do {
Transaction* tx = current->transaction;
if ( tx->amount == amt )
return tx;
current = current->next;
} while ( current != NULL );
return NULL; }

11. Search By Description
Transaction* searchDesc ( Node* list, string desc ) {
Node* current = list;
do {
Transaction* tx = current->transaction;
if ( tx->description == description )
return tx;
current = current->next;
} while ( current != NULL );
return NULL; }

12. Search By Transaction Search for a transaction you have a pointer to
int searchTxIndex ( Node* list, Transaction* tx1 ) {
Node* current = list;
int counter = 0;
do {
Transaction* tx = current->transaction;
if ( tx == tx1)
return counter;
current = current->next;
counter++;
} while ( current != NULL );
return -1; }

13. Retrieving Nodes By Index
Follow next until you reach the position
Transaction* getAt ( Node* list, int position ) {
Node* current = list;
int counter = 0;
do {
Transaction* tx = current->transaction;
if ( counter == position )
return tx;
current = current->next;
counter++;
} while ( current != NULL );
return NULL; }

14. Append to List Go to end and then link last to new
void append ( Node* list, Transaction* transaction ) {
Node* current = list;
do {
Transaction* tx = current->transaction;
current = current->next;
} while ( current->next != NULL );
Node* newNode = new Node;
newNode->next = NULL;
newNode->transaction = transaction;
current->next = newNode; }

15. Inserting At the Beginning of a List
Inserting a node has several cases
If inserting at 0, just push
void insertAt ( Node** list, Transaction* tx, int pos ) {
if ( pos == 0 ) {
push ( list, tx );
return; } …

16. Inserting Somewhere In the Middle
void insertAt ( Node** list, Transaction* txn, int pos ) { … Node* current = *list; int counter = 1; do { Transaction* tx = current->transaction; if ( counter == pos ) { Node* newNode = new Node; newNode->next = current->next; newNode->transaction = txn; current->next = newNode; return; } current = current->next; counter++; } while ( current->next != NULL );

17. Inserting at the End If inserting at the end, then just call append()
void insertAt ( Node** list, Transaction* tx, int pos ) {
if ( pos == 0 ) …
do { …
} while ( current->next != NULL );
append ( *list, tx ); }

18. Delete First Element
Deleting first element updates head to next and deletes
void deleteAt ( Node** list, int position ) {
if ( position == 0 ) {
Node* head = *list;
*list = (*list)->next;
delete head;
return; } …

19. Deleting In the Middle
void deleteAt ( Node** list, int position ) { … Node* prev = *list; Node* current = *list; current = current->next; int counter = 1; do { if ( counter == position ) { Node* deleteNode = current; prev->next = current->next; delete deleteNode; return; } prev = current; current = current->next; counter++; } while ( current->next != NULL ); …

20. Deleting At the End
If deleting the last, update next to last's next to NULL
void deleteAt ( Node** list, int position ) { …
prev->next = NULL;
delete current; }

21. LinkedListAlgorithmsDemo.cpp