Prepared by Dr. Inayatullah Shah1 Data Structures CSC212

Prepared by Dr. Inayatullah Shah2 Data Types & Data Structures Applications/programs read, store and operate on data. Finally output results. What is data? Numbers, Characters, etc. Application/ Program Data

Prepared by Dr. Inayatullah Shah3 Data Types & Data Structures Data is classified into data types. e.g. char, float, int, etc. A data type is (i) a domain of allowed values and (ii) a set of operations on these values.

Prepared by Dr. Inayatullah Shah4 Data Types & Data Structures Examples Data TypeDomainOperations boolean0,1and, or, =, etc. charASCII=, <>, <, etc. integer-maxint to +maxint +, _, =, ==, <>, <, etc.

Prepared by Dr. Inayatullah Shah5 Data Types & Data Structures int i,j;  i, j can take only integer values and only integer operations can be carried out on i, j. Built-in types: defined within the language e.g. int,float, etc. User-defined types: defined and implemented by the user e.g. using typedef.

Prepared by Dr. Inayatullah Shah6 Data Types & Data Structures Simple Data types: also known as atomic data types  have no component parts. E.g. int, char, float, etc ‘a’

Prepared by Dr. Inayatullah Shah7 Data Types & Data Structures Structured Data types: can be broken into component parts. E.g. record, array, set, file, etc. Example: a student record. AHMAD 20 CSC Name Age Branch A Component part

Prepared by Dr. Inayatullah Shah8 Data Types & Data Structures A data structure is a data type whose values (i) can be decomposed into a set of component elements each of which is either simple (atomic) or another data structure (ii) include a structure involving the component parts.

Prepared by Dr. Inayatullah Shah9 Data Types & Data Structure Possible Structures: Set, Linear, Tree, Graph. SET LINEAR TREE GRAPH

Prepared by Dr. Inayatullah Shah10 Data Types & Data Structures What is the domain of a structured data type? Operations? Example: boolean Sample[3]; Domain 100

Prepared by Dr. Inayatullah Shah11 Data Types & Data Structures Example: Operations: Sample[0] = 1; C = Sample[1]; etc. Elements Structure Domain Operations Data Type/ Structure

Prepared by Dr. Inayatullah Shah12 Abstract Data Types (ADTs) Abstraction? Hides details, provides only the essentials. Example: an integer 165 = , procedures/subprograms, etc. Abstract Data Types (ADTs): Simple or structured data types whose implementation details are hidden…

Prepared by Dr. Inayatullah Shah13 ADTs Questions about data types: –(i) What values are in the domain? What operations can be performed on the values of a particular data type? –(ii) How is the data type represented? How are the operations implemented?

Prepared by Dr. Inayatullah Shah14 ADTs ADTs specification answers the ‘what’ questions. Done first. ADTs implementation answers the ‘how’ questions. Done after specification. Users & Implementers. Users of an ADT need only know the specification …. no implementation details.  advantage Programmer who implements ADT is concerned with..specification, representation, implementation.

Prepared by Dr. Inayatullah Shah15 ADTs Elements Structure OperationsDomain Specification Representation Implementation User of an ADT must only know this Implementer must know all these.

Prepared by Dr. Inayatullah Shah16 ADT: Example ADT String1 Design (Specification): Elements: One character. Structure: elements (characters) are linearly arranged. Domain: There are 0 to 80 chars in a string, therefore … possible strings in the domain. Operations: 1. Append (c: char) Requires: The length of the string must be less than 80. Results: c is appended to the right end of the string.

Prepared by Dr. Inayatullah Shah17 ADT: Example 2. Remove Requires: The length of the string must be greater than 0. Results: The rightmost character of the string is removed and it is returned as the output of this operation. The string’s length is decreases by MakeEmpty Requires: The length of the string must be less than 80. Results: all characters are removed. 4. Concatenate (R: String) Results: A string R is concatenated to the right of the string. 5. Reverse 6. Length 7. Equal (R: String) 8. GetChar (int i) Requires: The length of the string must be greater than or equal to i. Results: Return the i-th character in the string.

Prepared by Dr. Inayatullah Shah18 Note.. In Java the class construct is used to declare new data types. In Java operations are implemented as methods.

Prepared by Dr. Inayatullah Shah19 ADT Representation in Java public class String1 extends Object { private char[] str; private int size; public void Append (char c) { }

Prepared by Dr. Inayatullah Shah20 ADT Representation in Java public char Remove (){ } public char GetChar(int i){ } public void MakeEmpty (){ } public int Length (){ }

Prepared by Dr. Inayatullah Shah21 ADT Representation in Java public void Concatenate (String1 s){ } public boolean Equal (String1 s){ } public void Reverse () { }

Prepared by Dr. Inayatullah Shah22 ADT Implementation in Java public class String1 extends Object { private char[] str; private int size; public String1 () { size = 0; str = new char[80]; } public void Append (char c) { str[size] = c; size++; }

Prepared by Dr. Inayatullah Shah23 ADT Implementation in Java public char Remove (){ size--; return(str[size]); } public char GetChar(int i){ return(str[i-1]); } public void MakeEmpty (){ size = 0; } public int Length (){ return(size);}

Prepared by Dr. Inayatullah Shah24 ADT Implementation in Java public void Concatenate (String1 s){ char c; for (int i = 0; i<s.Length(); i++) { c = s.GetChar(i+1); Append(c); } And we do the same thing for all other methods.

Prepared by Dr. Inayatullah Shah25 ADT Implementation in Java import java.lang.*; public class Test { public static void main(String[] args) { String1 s = new String1(); String1 s1 = new String1(); System.out.println("Hello, World"); s.Append('a'); s1.Append('b'); s.Concatenate(s1); System.out.print(s.GetChar(1)); System.out.println(s.GetChar(2)); }