presentation of data structure and algorithm

Decision making
statements in C
Presented by: Omair Aquil - 35000323023
Bisweswar Mahato - 35000323013
Agnish Deyati - 35000323003

Introduction to decision making statements
Decision making statements in C
If statement
If….else statement
If….else if….else statement
Nested if statement
Switch statement
The conditional operator(? : )
GOTO statement
References
Queries

Introduction to decision making statement in
C
Also known as control statements
Controls the flow of execution
Executes program until a specified condition is met
One of the most important parts in programming

Decision making statements in C
if statement
switch statement
Conditional operator statement
goto statement

If statement
The expression must evaluate to true or false.
The “statement” can be a group of statements in braces:
Syntax:
if(expression)
{
Statement 1;
Statement 2;
}

#include<stdio.h>
#include<conio.h>
main( )
{
int n ;
printf ( "Enter your age:
" ) ; scanf ("%d", &n ) ;
if ( n>=20 )
{
printf (“nYou are in your
adulthood. ” ) ;
}
getch();
}
Enter any number: 25
You are in your adulthood.

If else statement

An extension version of if statement.

Generally in the form of if (test
expression)
if (test expression)
{
true block statement(s)
}
else
{
false block statement(s)
}

Example
#include<stdio.h>
#include<conio.h>
main()
{
int age;
printf("n
enter your
age:");
scanf("%d",&ag
e);
if(age>=18)
{
printf("eligible for citizenship");
}
else
{
printf("n NOT ELIGIBLE");
}
getch();
}
enter your age:13
NOT ELIGIBLE
enter your age:20
eligible for citizenship

If …else if…. else statement

It is used to give series of decision

Syntax: if (condition)
{
//statement 1
}
else if (condition 2)
{
//statement 2
}
else
{
// statement when all condition are false
}

#include<stdio.h>
#include<conio.h>
#include<math.h>
void main()
{
float
a,b,c,d,r1,r2;
printf("Enter
coefficients a,
b and c: ");
scanf("%f%f%f",&a,&b,&c);
d=b*b-4*a*c;
if(d==0)
{
r1=-b/(2*a);
printf("n Roots are
equal and is %.3f",r1);
}
else if(d>0)
{
d=sqrt(d);
r1=(-b+d)/(2*a);
r2=(-b-d)/(2*a);
printf("nRoots are real and r1=%.3f, r2=%.3f",r1,r2);
}
else
{
d=sqrt(fabs(d));
printf("n Roots are imaginary");
printf("n r1=%.3f + i%.3f",-b/(2*a),d/(2*a));
printf("n r2=%.3f - i%.3f",-b/(2*a),d/(2*a));
}
getch();
//Program to find the roots of the quadratic equations
ax^2+bx+c=0
Enter coefficients a, b, c: 1
2
1
Roots are equal and is -1.000

Nested if-else statement
New block of if-else statement defined
in existing if or else block statement.
Syntax:
if(condition)
{
if(condition)
{
statement
}
else
{
statement
}
}
else
{
statement
}

#include <stdio.h>
#include <conio.h>
void main( )
{
int a,b,c;
printf("Enter 3 numbers: n");
scanf("%d%d%d",&a,&b,&c);
if(a>b)
{
if( a > c)
{
printf(“%d is greatest“,a);
}
else
{
printf(“%d is greatest“,c);
}
}
else
{
if( b> c)
{
printf(“%d is
greatest“,b);
}
else
{
printf(“%d is
greatest“,c);
}
}
Using Nested-if statement to check greatest
number among three input numbers
Enter 3 numbers:
9
11
5
11 is greatest
Enter 3 numbers:
49
55
88
88 is greatest

 Multi-way decision statement
Tests the value of a given variable against a list of case values
 when a match is found, a block of statements associated with
that case is executed.

switch (var)
{
case case value 1:
statements;
break;
case case value 2:
statements;
break;
…….
…….
case case value n:
default:
statements;
break;
}
Should be an integer or characters
Known as case labels and should be constants or
constant expressions
And should be end with semicolon

#include<stdio.h>
int main()
{
char operator;
float firstNumber,secondNumber;
printf("Enter an operator (+, -): ");
scanf("%c", &operator);
printf("Enter two operands: ");
scanf("%f %f",&firstNumber,
&secondNumber);
switch(operator)
{ case '+':
printf("%f + %f = %f",firstNumber, secondNumber, firstNumber +
secondNumber);
break;
case '-':
printf("%f - %f = %f",firstNumber, secondNumber, firstNumber -
secondNumber);
break;
default:
printf("Error! operator is not correct");
}
return 0;
}
Enter an operator(+,-): -
Enter two operands: 6
4
6.000000 – 4.000000 = 2.000000
Enter an operator(+,-): /
Enter two operands: 9
3
Error! operator is not correct

The ?: operator
Known as conditional operator
Used for making two-way decisions
Syntax:
Conditional expression ? exp1: exp2

Example:
//If True first exp is executed
//If False second exp is executed
#include <stdio.h>
#include <conio.h>
#include <math.h>
void main()
{
int a;
printf("Enter a number: ");
scanf("%d",&a);
(a%2==0?printf("Even"):printf("Odd"));
getch();
}
Enter
Odd
a number: 9
Enter
Even
a number: 8

The GOTO statement
Rarely used statement
 Provides an unconditional jump from ‘goto’ to a labelled
statement in the same function
Syntax:
Requires label to identify the place where the branch is to be made
goto label;
-------------
-------------
label;
statement;
label;
statement;
------------
-
------------
-
goto
label;
Forward jump Backward jump

Example:
#include <stdio.h>
#include <conio.h>
#include <math.h>
void main()
{
float y,x;
read:
printf("nEnter a number: ");
scanf("%f",&y);
if(y<0) goto read;
x=sqrt(y);
printf("nSquare
root of %f---->%f
n",y,x);
goto read;
}
Enter a number: 9
Square root of 9.000000---->3.000000
Enter a number: 25
Square root of 25.000000----
>5.000000

References:
Websites:
google.com
codecadamy.com
tutorialspoint.com
External sources:
Text book: Programming in ANSIC (E-Balagurusamy)

presentation of data structure and algorithm

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