A list is a linear collection of elements with a relationship between consecutive elements. It supports basic operations like insertion, deletion, and retrieval of elements. This document discusses the implementation of an unsorted list data structure using both array-based and linked representations. Specifically, it describes: - The key differences between array and linked implementations - How insertion, deletion, and retrieval are implemented for linked lists - The node struct and list class used in the linked implementation

1. What is a List? A list is a homogeneous collection of elements, with a linear relationship between elements. That is, each list element (except the first) has a unique predecessor, and each element (except the last) has a unique successor.

2. ADT Unsorted List Operations Transformers MakeEmpty InsertItem DeleteItem Observers IsFull LengthIs RetrieveItem Iterators ResetList GetNextItem change state observe state process all

3. // SPECIFICATION FILE ( unsorted.h ) class UnsortedType // declares a class data type { public : // 8 public member functions …… private : // 3 private data members // 리스트를 배열로 표현 int length ; ItemType info[MAX_ITEMS] ; // MAX_ITEMS 은 상수임 int currentPos ; // Linked List 구현 private : NodeType* listData; int length; NodeType* currentPos; } ; ADT Unsorted List 의 Linked 리스트 구현 struct ItemType { … . KeyType key; … };

4. class UnsortedType MakeEmpty ~UnsortedType DeleteItem . . . InsertItem UnsortedType RetrieveItem GetNextItem ‘ X’ ‘C’ ‘L’ Private data: length 3 listData currentPos ?

5. Linked Implementation 다음 세 가지의 차이점 ? location , *location , 과 location->info

6. s truct NodeType { ItemType info; NodeType* next; }; class UnsortedType { public : // LINKED LIST IMPLEMENTATION UnsortedType ( ) ; ~UnsortedType ( ) ; void MakeEmpty ( ) ; bool IsFull ( ) const ; int LengthIs ( ) const ; void RetrieveItem ( ItemType& item, bool& found ) ; void InsertItem ( ItemType item ) ; void DeleteItem ( ItemType item ) ; void ResetList ( ); void GetNextItem ( ItemType& item ) ; private : NodeType* listData; int length; NodeType* currentPos; } ;

7. // LINKED LIST IMPLEMENTATION ( unsorted.cpp ) #include “itemtype.h” template <class ItemType> UnsortedType<ItemType>::UnsortedType ( ) // constructor // Pre: None. // Post: List is empty. { length = 0 ; listData = NULL; } template <class ItemType> int UnsortedType<ItemType>::LengthIs ( ) const // Post: Function value = number of items in the list. { return length; }

8. Linked Implementation: RetrieveItem

9. template <class ItemType> void UnsortedType<ItemType>::RetrieveItem( ItemType& item, bool& found ) // Pre: Key member of item is initialized. // Post: If found, item’s key matches an element’s key in the list // and a copy of that element has been stored in item; otherwise, // item is unchanged. { bool moreToSearch ; NodeType<ItemType>* location ; location = listData ; found = false ; moreToSearch = ( location != NULL ) ; while ( moreToSearch && !found ) { if ( item .key == location->info .key ) // match here { found = true ; item = location->info ; } else // advance pointer { location = location->next ; moreToSearch = ( location != NULL ) ; } } }

10. template <class ItemType> void UnsortedType<ItemType>::InsertItem ( ItemType item ) // Pre: list is not full and item is not in list. // Post: item is in the list; length has been incremented. { NodeType<ItemType>* location ; // obtain and fill a node location = new NodeType<ItemType> ; location->info = item ; location->next = listData ; listData = location ; length++ ; }

11. Inserting ‘B’ into an Unsorted List Private data: length 3 listData currentPos ? ‘ X’ ‘C’ ‘L’

12. location = new NodeType<ItemType>; Private data: length 3 listData currentPos ? item location ‘ B’ ‘ X’ ‘C’ ‘L’

13. location->info = item ; Private data: length 3 listData currentPos ? item location ‘ B’ ‘ B’ ‘ X’ ‘C’ ‘L’

14. location->next = listData ; Private data: length 3 listData currentPos ? item location ‘ B’ ‘ B’ ‘ X’ ‘C’ ‘L’

15. listData = location ; Private data: length 3 listData currentPos ? item location ‘ B’ ‘ B’ ‘ X’ ‘C’ ‘L’

16. length++ ; Private data: length 4 listData currentPos ? item location ‘ B’ ‘ B’ ‘ X’ ‘C’ ‘L’

17. Linked Implementation: DeleteItem How do you delete an item from the list? Find the item Remove the item

18. template <class ItemType> void UnsortedType<ItemType>:: Delete Item ( ItemType item ) // Pre: An element in the list has a key that matches item’s. // Post: No element in the list has a key that matches item’s. { NodeType<ItemType>* location = listData ; NodeType<ItemType>* tempLocation; // Locate node to be deleted. if (item.key == listData->info.key) { tempLocation = location; listData = listData->next; } else { while(!(item.key == (location->next)->info.key)) location = location->next; // Delete node at location->next. tempLocation = location->next; location->next = location->next->next; } delete tempLocation; length--; }

19. template <class ItemType> void UnsortedType<ItemType>::ResetList() { currentPos = NULL; } template <class ItemType> void UnsortedType<ItemType>::GetNextItem(ItemType& item) { if (currentPos == NULL) currentPos = listData; else currentPos = currentPos->next; item = currentPos->info; }

20. template <class ItemType> UnsortedType<ItemType>::~UnsortedType() { NodeType<ItemType>* tempPtr; while(listData != NULL) { tempPtr = listData; listData = listData->next; delete tempPtr; } }