114 3/30/98 CSE 143 Collection ADTs [Chapter 4]

115 3/30/98 Collection ADTs  Many standard ADTs are for collections  Data structures that manage groups of data  Some terms:  Order of data: Linear vs. Nonlinear (list vs. set)  Method of access: Direct vs. Sequential  Type of data: Homogenous vs. Heterogeneous  Size: Fixed vs. Variable

116 3/30/98 Classification of ADTs Collections Ordered CollectionsUnordered Collections Array List Queue Stack Record Set DirectSequential Bag HeterogeneousHomogeneous Table

117 3/30/98 Collections in C++  Direct support for records ( struct / class ) and arrays  Other ADTs must be implemented  No absolute standards  Many conventional operations and concepts  Standard (Template) Library (new)  contains many ADTs  Our Plan:  Look at each ADT  Learn the conventional operations  Consider possible implementations

118 3/30/98 Arrays as ADTs [Section 4.3]  Attributes of array type:  Linear sequence of homogeneous elements  Fixed length  Direct access  Operations on arrays  Direct indexing using [] operator  Built in arrays provide no bounds checking  No searching, sorting, insertion, etc.

119 3/30/98 Record ADT [Section 4.4]  Attributes of record type:  Nonlinear collection of heterogeneous elements (fields)  Fixed number of elements  Direct access  Operations on records  Accessing elements directly through. operator  We’ll typically use classes to implement records, providing encapsulation via access functions.  In C++, structs are classes where members are public (by default)

120 3/30/98 List ADT [Section 4.5]  Attributes of list type:  Linear sequence of homogeneous elements  Varying number of elements  Sequential access  Operations on lists  Sequential access through a “cursor”  Test if full, empty, cursor at end  Insert, delete elements

121 3/30/98 List Terminology  Head: First element in list  Tail: Last element in list  Cursor: “Current” element of list  Size: Number of elements in list aList: HeadTail Cursor elem 0 elem 1 elem 2 elem N-1... (Size=N)

122 3/30/98 Lists in C++  No predefined list type, so write our own  Use the class construct  Member functions for list operations  Private data for list representation  We’ll look at a list of integers, but later we’ll see how to write more general kinds of lists (or other ADTs).

123 3/30/98 List Interface // In IntList.h const int MAX_SIZE = 20; class IntList { public: IntList ();// Create an empty list int data ();// get data item // (the one pointed to by cursor) bool isEmpty ();// Is the list empty? bool isFull ();// can add more elements? int sizeOf(); void reset ();// move cursor to head void advance();// advance cursor bool endOfList(); // cursor past the end?

124 3/30/98 List Interface (2) // insert the item before the cursor. void insertBefore(int item); // insert the item after cursor. void insertAfter(int item); void deleteItem(); // delete the private: int items[MAX_SIZE]; int last; // position of last element int cursor; // position of current element };

125 3/30/98 List Implementation (1) #include “IntList.h” IntList::IntList() { cursor = -1; last = cursor; } bool IntList::isEmpty() { return (sizeOf() == 0); } bool IntList::isFull() { return (sizeOf() == MAX_SIZE); }

126 3/30/98 List Implementation (2) int IntList::sizeOf() { return last+1; } void IntList::reset() { cursor = 0; } void IntList::advance() { assert(!endOfList()); cursor++; } bool IntList::endOfList() { return (cursor > last); }

127 3/30/98 List Implementation (3) int IntList::data() { assert (!endOfList()); return items[cursor]; } void IntList::insertBefore(int item) { assert (!isFull()); if (last == -1) cursor = 0; else for (int i=last; i>=cursor; i--) items[i+1] = items[i]; items[cursor] = item; last++; }

128 3/30/98 List Implementation (4) void IntList::insertAfter(int item) { assert(!isFull() && !endOfList()); for (int i=last; i>= cursor+1; i--) items[i+1] = items[i]; items[cursor+1] = item; last++; cursor++; } void IntList::deleteItem() { for (int i=cursor; i < last; i++) items[i] = items[i+1]; last--; }

129 3/30/98 Client of List #include “IntList.h” void main() { IntList grades; int aGrade; while (cin >> aGrade) grades.insertAfter(aGrade); for (grades.reset(); !grades.endOfList(); grades.advance()) cout << grades.data() << endl; }

130 3/30/98 Summary  Collection ADTs  Distinguished by order, access, types of data  Arrays:  ordered, direct access by index, homogeneous  Records:  unordered,direct access by name, heterogeneous  Lists:  ordered, sequential access, homogeneous  Head, Tail, Cursor  size(), isEmpty(), isFull()  reset(), endOfList(), advance(), data()  insertBefore(), insertAfter(), deleteItem()