1

Reference  2

 Algorithm :- Outline the essence of a computational procedure, step by step instructions.  Program :- an implementation of an algorithm in some programming language  Data Structure :- Organization of data needed to solve the problem. 3

Algorithm: Finite set of instructions that, if followed, accomplishes a particular task. Describe : Representation of algorithm can written By :- in natural language ( English ) / pseudo-code / diagrams / etc. 4

Any computing algorithm will have AT MOST five kinds of components: Data structures to hold data Instructions change data values Conditional expressions to make decisions Control structures to act on decisions Modules to make the algorithm manageable by abstraction, i.e., grouping related components 5

6 Relations between Problems, Algorithms and Programs Problem Algorithm Program....

What is a Good Algorithm ?  Efficient :-  Running Time  Space Used  Efficiency as function of input size :-  The number of bits in an input number  Number of data elements ( numbers, points ) 7

8 W ORST - / AVERAGE - / BEST - CASE Worst-case running time of an algorithm  The longest running time for any input of size n  An upper bound on the running time for any input  guarantee that the algorithm will never take longer  Example: Sort a set of numbers in increasing order; and the data is in decreasing order  The worst case can occur fairly often E.g. in searching a database for a particular piece of information Best-case running time sort a set of numbers in increasing order; and the data is already in increasing order Average-case running time Average number of steps taken on any instance of size n

9 Pseudo- code :- A mixture of natural language and high – level programming concepts that describes the main ideas behind a generic implementation of a data structure or algorithm Eg:- Algorithm arrayMax ( A, n ) input : An array A sorting n integers Output : The Maximum element in A currentMax A[0] for i 1 to n-1 do if currentMax < A[i] then currentMax A[i] return currentMax

Pseudo – Code It is more structured than usual language but less formal than a programming language. Expressions :  Use standard mathematical symbols to describe numeric and Boolean expression.  Use for assignment ( “=“ in java )  Use = for the equality relationship( “==“ in java ) 10

Pseudo- Code  Programming Constructs :-  decision structures :- if …. Then … [ else ]  while – loops : while.. Do  repeat – loops : repeat … until..  for – loop : for.. Do  array indexing : A[i], A[I,j]  Methods :  Calls : object method ( args )  returns : return value 11

Simple Algorithm Find sum n numbers between any given range numbers 1- Start 2- Read N 3- Sum =0 4- For I= 1 to N 4.1 sum = sum + I 4.1 next I 5- print Sum 6- End 12

Basic Structure of C++ Language 13 Documentation Section Link Section Definition Section Global Declaration Section Subprogram Section Function 1 ….. Function n main(){ Declaration Section Executable Section }

14 Language Built-inUser-defined Data Operators Assignment ( = ) Arithmetic (+,-,*,/,%) Relational (, >=,==,!=) Logical (&&, ||) Unary (++, --) DataOperators Atomic int (2 bytes) char (1 byte) float (4 bytes) double (8 bytes)

Tokens The smallest element in the C language is the token. Tokens can be: Numeric constants : 123, 98.6, Character constants : ‘A’, ‘a’, ‘$’, ‘4’ String constants : “UMBC”, “I like ice cream.”, “123”, “CAR”, “car” Keywords : int, while, for Names (identifiers) Punctuation : ; :, ‘ “ [ ] { } ( ) Operators: =, +, -, *, /, <>,, >=, !=, &&, ||, ++, --

Simple C++Program /*---- Hello World C Example ("hello.c") */ /* ANSI C Headers */ #include /* Main Program starts here */ void main ( ) { int i = 0; /* End of declarations... */ for ( i = 0; i < 10; i++ ) { cout<<“ Hello World”<<endl<< i ); /* print to standard output */ } 15 Include headers if you need to use functions in these files Comment: /*.. */ Declare all your variables first

Control Statement SelectionIterationJump IfForBreak SwitchWhileContinue …………Do- whileReturn 16

Eg:- to calculate the average of n number /*Calculate the average of n numbers*/ #include void main(){ int n, count=1; float x, average,sum=0; cout<<"Enter the limit”<<endl; /*initialize and read in a value for n*/ cin>>n; while(count<=n) /*Read in the numbers*/ { cout<<"x= “; cin>>x; sum+=x; ++count; } /*calculate the average and display result*/ average=sum/n; cout<<“The average is ”<<average; getch();} 17

While Syntax :- While (Expression ) { Statement (s ) Increment counter } Do – while Syntax :- Do { statement(s) Counter } While(expression ); 18

Functions A function is a self contained program segment that carries out some specific,well-defined task. C regards main() as function Functions should be defined separately before or after main. A function will process information that is passed to it from the calling program and return a single value Each function contains: A function heading (function name), followed by optional list of arguments enclosed in parentheses. A list of argument declarations A compound statement enclosed within a pair of braces { } 19

Functions Cont.. Function Definition: returntype fn_name(type1 arg1,type2 arg2, …..type n,arg n) { localvariables functioncode } Example: int maximum(int x, int y) { int z; z=(x>=y) ? x:y; return(z);} Calling A function: function-name(arg1,arg2,….arg n); Function Prototype: returntype fn_name(type1 arg1,type2 arg2, …..type n,arg n);

C ++ Program illustrating Function /*Program to calculate the area of a circle*/ #include const float PI= 3.14; float areacircle( float radius) ; /* function prototype*/ main() { float radius, area; cout<<"Enter value of radius“<<endl; cin>>radius; area=areacircle(radius); /* call function */ cout<<“Area= “<<area ; getch(); } float areacircle(float r) { /* definition of function */ a= PI*r*r; return(a); } 20

Assignment -1- Write algorithm for the following  sum of n numbers between given range ( Using while )  sum of n numbers between given range ( Using Do… while )  count even& odd numbers in given range( Using For )  count even & odd numbers in given range( Using while )  count even & odd numbers in given range(Using Do.. while) 21