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Data Structure

Data Structure. Dr. Mohamed Khafagy. Abstraction. . Abstraction is a technique in which we construct a model of an entity based upon its essential Characteristics while ignoring the inessential details. . The principle of abstraction also helps in handling the

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Data Structure

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  1. Data Structure Dr. Mohamed Khafagy

  2. Abstraction . Abstraction is a technique in which we construct a model of an entity based upon its essential Characteristics while ignoring the inessential details. . The principle of abstraction also helps in handling the inherent complexity of a system by allowing looking at its important external characteristic, and hiding its inner complexity at the same time. . Hiding the internal details is called encapsulation. . Engineers of all fields, including computer science, have been practicing abstraction for mastering complexity.

  3. Types of data Abstraction . Code and Data abstraction • What is Data ? - What is code ?

  4. Advantages of data Abstraction • Simplification of software development • Testing and Debugging • Reusability • Modification to representation of a data type • etc

  5. void selectionSort(int a[],int size){ int I,j,min,temp; for(i=0; i<size-1; i++) { min=i; for(j=i; i<size; j++) { if(a[j]< a[min]) min=j; } temp=a[i]; a[i]=a[min]; a[min]=temp; }}

  6. void swap(int &x, int &y) { inttemp=x; x=y; y=temp; } int minimum(int a[],intfrom,int to) { int min=from; for(inti=from;i<=to;i++) if(a[i] < a[min]) min=i; return min; } void selectionSort(int a[],int size) { inti,j,min; for(i=0;i<size-1;i++){ min=minimum(a,I,size-1) swap(a[i],a[min]); } }

  7. Data Abstraction and Abstract Data Types(ADT) • A data type is a template for objects and a set of operations that define the behavior of the objects (or instances) of that type. • An Abstract data type (ADT) is a data type in which the implementation details are hidden and the user is concerned with the properties ( or behavior ) of that type. • An ADT has two commponents: - Interface – the behavior - Implementation • Example: -int,float

  8. Abstract Data Type • The data structures used to implement the data type can only be accessed through the interface. • Any change in the implementation does not change the user programs as long as the interface remains the same. • This is also known as data encapsulation or data abstraction. interface1 interfece2 implementation interface3 interface4

  9. Abstraction Vs.Implementation • X -> 01000001 01000010 01000011 00000000 • X = ? • If x is CString -then x -> “ABC” • If x is integer - then x -> 1094861568

  10. Abstraction Vs. ImplementationTwo dimensional array User’s view (abstraction) System’s view (implementation)

  11. ADTs and C++ Classes • A class is used to define (and implement) an ADT in C++. • A class consists of data and functions that operate on that data. • A class in C++ has two parts – public and private (let’s ignore the protected members for now). • The data and functions defined in the class are called the members of the class.

  12. ADTs and C++ Classes • Users of the class can only access and manipulate the class state through the public members of the class. • Private members can only be used by other members of the class (let’s also ignore the friends for now). • Data encapsulation is achieved by declaring all data members of a class to be private. • The interface of the class is provided through the use of public member functions.

  13. Data Structures • The primary objective of programming is to efficiently process the input to generate the desired output. • We can achieve this objective in an efficient and neat style if the input data is organized in a way to help us meet our goal. • Data Structures is nothing but ways and means of organizing data so that it can be processed easily and efficiently. • Data structures dictate the manner in which the data can be processed. In other words, the choice of an algorithm depends upon the underlying data organization. ( What is an Algorithm ? )

  14. Data Structure Operations • Traversing • Searching • Inserting • Deleting • Sorting • Merging • Recursion • To perform operations on various data structures we use algorithms.

  15. Types of Data Structures • Premitive/Scalar : data types that can be manipulated as a single quantity or can be represented alone • Structured/ Non-Premitive (Data type which is collection of other premitive or non-premitive data structures. • Can be further divided into a) linear b) non-linear - Linear can be further split into a) physically linear b) logically linear

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