C++ Programing : C++ If else programs
C++ Programing : C++ If else programs
1) Check Whether Number is Even or Odd
Method 1: Using if else
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter an integer: ";
cin >> n;
if ( n % 2 == 0)
cout << n << " is even.";
else
cout << n << " is odd.";
return 0;
}
Output
Enter an integer: 23
23 is odd.
Method 2: Using ternary operators
#include <iostream>
using namespace std;
int main() {
int n;
cout << "Enter an integer: ";
cin >> n;
(n % 2 == 0) ? cout << n << " is even." : cout << n << " is odd.";
return 0;
}
CONCEPT:
We used ternary operators ?: instead of if..else statement. The ternary operator is a
shorthand notation of if...else statement.
2) Check Whether a character is Vowel or Consonant.
CODE:
#include <iostream>
using namespace std;
int main() {
char c;
bool isLowercaseVowel, isUppercaseVowel;
cout << "Enter an alphabet: ";
cin >> c;
// evaluates to 1 (true) if c is a lowercase vowel
isLowercaseVowel = (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u');
// evaluates to 1 (true) if c is an uppercase vowel
isUppercaseVowel = (c == 'A' || c == 'E' || c == 'I' || c == 'O' || c == 'U');
// show error message if c is not an alphabet
if (!isalpha(c))
printf("Error! Non-alphabetic character.");
else if (isLowercaseVowel || isUppercaseVowel)
cout << c << " is a vowel.";
else
cout << c << " is a consonant.";
return 0;
}
Output
Enter an alphabet: u
u is a vowel.
CONCEPT:
The isalpha() function checks whether the character entered is an alphabet or not. If it is
not, it prints an error message.
3) Program to Find Largest Number Among Three Numbers
Method 1: Using if...else Statement
#include <iostream>
using namespace std;
int main() {
float n1, n2, n3;
cout << "Enter three numbers: ";
cin >> n1 >> n2 >> n3;
if((n1 >= n2) && (n1 >= n3))
cout << "Largest number: " << n1;
else if ((n2 >= n1) && (n2 >= n3))
cout << "Largest number: " << n2;
else
cout << "Largest number: " << n3;
return 0;
}
Output
Enter three numbers: 2.3
8.3
-4.2
Largest number: 8.3
Method 2: Using Nested if...else statement
Code:-
#include <iostream>
using namespace std;
int main() {
float n1, n2, n3;
cout << "Enter three numbers: ";
cin >> n1 >> n2 >> n3;
if (n1 >= n2) {
if (n1 >= n3)
cout << "Largest number: " << n1;
else
cout << "Largest number: " << n3;
}
else {
if (n2 >= n3)
cout << "Largest number: " << n2;
else
cout << "Largest number: " << n3;
}
return 0;
}
Output
Enter three numbers: 2.3
8.3
-4.2
Largest number: 8.3
4) Program to Find All Roots of a Quadratic Equation
CODE:
#include <iostream>
#include <cmath>
using namespace std;
int main() {
float a, b, c, x1, x2, discriminant, realPart, imaginaryPart;
cout << "Enter coefficients a, b and c: ";
cin >> a >> b >> c;
discriminant = b*b - 4*a*c;
if (discriminant > 0) {
x1 = (-b + sqrt(discriminant)) / (2*a);
x2 = (-b - sqrt(discriminant)) / (2*a);
cout << "Roots are real and different." << endl;
cout << "x1 = " << x1 << endl;
cout << "x2 = " << x2 << endl;
}
else if (discriminant == 0) {
cout << "Roots are real and same." << endl;
x1 = -b/(2*a);
cout << "x1 = x2 =" << x1 << endl;
}
else {
realPart = -b/(2*a);
imaginaryPart =sqrt(-discriminant)/(2*a);
cout << "Roots are complex and different." << endl;
cout << "x1 = " << realPart << "+" << imaginaryPart << "i" << endl;
cout << "x2 = " << realPart << "-" << imaginaryPart << "i" << endl;
}
return 0;
}
Output
Enter coefficients a, b and c: 4
5
1
Roots are real and different.
x1 = -0.25
x2 = -1
CONCEPT:
In this program, sqrt() library function is used to find the square root of a number.
5) Program to Calculate Sum of first N Natural Numbers
We have to display the value of 1+2+3+....+N.
CODE:
#include <iostream>
using namespace std;
int main() {
int n, sum = 0;
cout << "Enter a positive integer: ";
cin >> n;
for (int i = 1; i <= n; ++i) {
sum += i;
}
cout << "Sum = " << sum;
return 0;
}
Output
Enter a positive integer: 50
Sum = 1275
NOTE: If a user enters a negative number, Sum = 0 is displayed and program is
terminated.
6) Program to Check Leap Year
CODE:
#include <iostream>
using namespace std;
int main() {
int year;
cout << "Enter a year: ";
cin >> year;
if (year % 4 == 0) {
if (year % 100 == 0) {
if (year % 400 == 0)
cout << year << " is a leap year.";
else
cout << year << " is not a leap year.";
}
else
cout << year << " is a leap year.";
}
else
cout << year << " is not a leap year.";
return 0;
}
Output
Enter a year: 2014
2014 is not a leap year
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