CSCE 110 PROGRAMMING FUNDAMENTALS WITH C++

1. CSCE 110PROGRAMMINGFUNDAMENTALSWITH C++ Prof. Amr Goneid AUC Part 15. Dictionaries (1): A Key Table Class Prof. amr Goneid, AUC

2. Dictionaries(1): A Key Table Class Prof. Amr Goneid, AUC

3. A Key Table Class • The Key Table as a Dictionary • ADT Key Table • Key Table Data Members • Key Table Operations • Class Template • Element Specification • Key Table Class Definition • Key Table Class Implementation • Example Application Prof. Amr Goneid, AUC

4. 1. The Key Table as a Dictionary • A key table is essentially a DictionaryADT. • A form of container that permits access by content. An element (e) has a key part (k) • Supports the following main operations: • Insert (D, e):Insert item e in dictionary D • Delete (D, e):Delete item e from D • Search (D, k):search for key k in D Prof. amr Goneid, AUC

5. 2. ADT Key Table • Key Table: a linear configuration of elements in which we can insert and delete such elements. It also supports search by content (key), and can represent a dictionary ADT. • Element: contains one key and associated data item • CurrentElement: special element in the table, indicated by a pointer to the currentposition. Prof. Amr Goneid, AUC

6. ADT Key Table • We will construct a class “Ktable” whose objects are key tables. A key table will be implemented as a dynamic array. • The data members will be the elements and a pointer (index) to these elements. • An element contains a key field and a data field. Search is by content (key) • The table will have a default maximum size MaxSize of 128 elements. The application program can specify other sizes since the table is dynamic. • The application program will also specify the actual types for the key and data fields. Prof. Amr Goneid, AUC

7. 3. Key Table Data Members • Elements. Each element has: • A key of type keyType • Data or information field of type dataType • Others: T, a pointer to a dynamic array of elements; P, a pointer (index) to the current element; MaxSize, The maximum size (Capacity) of the table N, index of the last element in the table ( N < 0 if the table is empty, and N = Maxsize – 1 if the table is full). Prof. Amr Goneid, AUC

8. 4. Key Table Operations • construct:Create table • destruct:Destroy table • tableIsEmpty  bool : return True if table is empty • tableIsFull  bool : return True if table is full • occupancy  int : return the current no. of elements in the table Prof. Amr Goneid, AUC

9. Key Table Operations • update (d) : to update the data portion of the currentelement to contain d; assume the current position is nonempty. • retrieve (d): to return the data (d) in the currentelement; assume the current position is nonempty. • delete: delete the currentelement. Assume the current position is nonempty initially. Prof. Amr Goneid, AUC

10. Key Table Operations • search (k)  bool : Search the table for the slot with key part that matches (k). If found, set p to the slot and return True, else return false • insert (k,d) : insert an element at the end of the table. • traverse: traverse table to print key and data fields. Prof. Amr Goneid, AUC

11. 5. Class Template • We will allow the class to receive the type of key and type of data stored in the class via parameters. • This is called a class template • We achieve this by doing the following: • In the header file, declare the template class with its parameters, e.g., template <class keyType, class dataType> class KTable { …….. }; Prof. amr Goneid, AUC

12. Class Template • In the implementation file, every function is preceded by the class template. • In the implementation file, the class name in a function header, is succeeded by the template <…>. Example: // return True if table is full template <class keyType, class dataType> bool Ktable <keyType, dataType>::tableIsFull() const { return (N == MaxSize-1); } Prof. amr Goneid, AUC

13. 6. Element Specification // The element structure can be specified as a Class // in the private part of the main Ktable class. class element // Hidden from user { public: keyType key; // key dataType data; // Data }; // end of class element declaration Prof. Amr Goneid, AUC

14. 7. Key Table Class Definition // File: Ktable.h // Definition of Ktable Template Class #ifndef KTABLE_H #define KTABLE_H // Specification of the class template <class keyType, class dataType> class Ktable { public: Prof. Amr Goneid, AUC

15. Key Table Class Definition // Member Functions Ktable(int nelements = 128); // Constructor ~Ktable(); // Destructor // Functions Prototype Definitions bool tableIsEmpty() const; bool tableIsFull() const; int occupancy() const; void update (const dataType & ); void retrieve (dataType &) const; void delete (); Prof. Amr Goneid, AUC

16. Key Table Class Definition bool search (const keyType & ); bool insert (const keyType &, const dataType & ); void traverse () const; private: // Element Class class element { public: keyType key; // key dataType data; // Data }; // end of class element declaration Prof. Amr Goneid, AUC

17. Key Table Class Definition element *T; // Pointer to Storage Array int p; // Pointer to current element // Maximum and index of last element int MaxSize, N; }; // end of Ktable Class definition #endif// KTABLE_H #include "Ktable.cpp" Prof. Amr Goneid, AUC

18. 8. Key Table Class Implementation // File:Ktable.cpp Class implementation file #include <iostream> using namespace std; // Constructor with argument, size is nelements, default is 128 template <class keyType, class dataType> Ktable<keyType, dataType> ::Ktable(intnelements) { MaxSize = nelements; T = new element[MaxSize]; p = -1; N = -1; } Prof. Amr Goneid, AUC

19. Key Table Class Implementation // Destructor template <class keyType, class dataType> Ktable <keyType, dataType> ::~Ktable() { delete [ ] T; } // return True if table is empty template <class keyType, class dataType> bool Ktable <keyType, dataType> ::tableIsEmpty() const { return (N < 0); } Prof. Amr Goneid, AUC

20. Key Table Class Implementation // return True if table is full template <class keyType, class dataType> bool Ktable <keyType, dataType> ::tableIsFull() const { return (N == MaxSize - 1); } // return the current occupancy of the table template <class keyType, class dataType> int Ktable <keyType, dataType> ::occupancy() const { return (N+1); } Prof. Amr Goneid, AUC

21. Key Table Class Implementation // to update the data in the current position template <class keyType, class dataType> void Ktable <keyType, dataType>::update (const dataType &d) { if ((p >= 0)&&(p <= N)) T[p].data = d; } // Retrieve the data part of the current position template <class keyType, class dataType> void Ktable<keyType, dataType>::retrieve (dataType &d) const { if ((p >= 0)&&(p <= N)) d = T[p].data; } Prof. Amr Goneid, AUC

22. Key Table Class Implementation // delete the current element. // After deletion, current element becomes empty template <class keyType, class dataType> void Ktable <keyType, dataType> ::delete () { if ((p >= 0)&&(p <= N)) { if (p < N) for (int i = p; i < N; i++) T[i] = T[i + 1]; N--; p = -1; } } Prof. Amr Goneid, AUC

23. Key Table Class Implementation // search the table for the element with key (k). // If found, set p to it and return True, else return false template <class keyType, class dataType> bool Ktable <keyType, dataType> ::search (const keyType &k) { bool found = false; p = -1; if(!tableIsEmpty()) { i = 0; while ((! found) && (i <= N)) if (k == T[i].key) { found = true; p = i ; } else i++; } return found; } Prof. Amr Goneid, AUC

24. Key Table Class Implementation // insert element at the end of the table template <class keyType, class dataType> bool Ktable <keyType, dataType> :: insert (const keyType &k, const dataType &d) { if (!tableIsFull()) { N++; T[N].key = k; T[N].data = d; return true ; } else return false; } Prof. Amr Goneid, AUC

25. Key Table Class Implementation // traverse table to print key and data fields template <class keyType, class dataType> void Ktable <keyType, dataType> ::traverse () const { for(int i = 0; i <= N; i++) cout << T[i].key << " " << T[i].data << endl; } Prof. Amr Goneid, AUC

26. 9. Example Application Build a list of characters and their frequencies in a string: Given a string, search for every character in a key table . If a character does not exist in the table, insert it with a count of 1, otherwise , increment its count. Prof. Amr Goneid, AUC

27. Character Frequency Table // File: KTabletest.cpp // Applies Ktable Class #include <iostream> #include <string> using namespace std; #include "Ktable.h“ int main() { Ktable <char , int> ctable (50); string s; char c; int i, count; bool keyfound; Prof. Amr Goneid, AUC

28. Character Frequency Table // Read a string cout << "Enter a string:" << endl; getline(cin,s); cout << s << endl; // display it for (i = 0; i < s.length(); i++) // for every character { c = toupper(s.at(i)); // Search for character in the table keyfound = ctable.search (c); Prof. Amr Goneid, AUC

29. Character Frequency Table if (keyfound) // if found { ctable.retrieve (count); // get data count++; // increment count ctable.update (count); // store back } // Not found, a new element is inserted else ctable.insert(c,1); } Prof. Amr Goneid, AUC

30. Character Frequency Table // print characters and their frequencies ctable.traverse(); // current table size cout << ctable,occupancy() << endl; // Free Memory ctable. ~Ktable(); return 0; } Prof. Amr Goneid, AUC

31. Sample Output Enter a string: The New View The New View T 1 H 1 E 3 2 N 1 W 2 V 1 I 1 8 Press any key to continue Prof. Amr Goneid, AUC