C and Java Programs for Even/Odd and Sum of N Natural Numbers

Check if a Number is Even or Odd in C

Given an integer input, the objective is to determine whether a number is even or odd using C programming.

An even number is completely divisible by 2, whereas an odd number leaves a remainder of 1 when divided by 2.

Sum of First N Natural Numbers (C and Java)

Natural numbers are a sequence of positive numbers starting from 1. The sum of the first N natural numbers can be calculated using different methods.

Method 1: Using Brute Force

public class Main {
    public static void main (String[] args) {
        int n = 10;
        int sum = 0;
        for (int i = 1; i <= n; i++)
            sum += i;
        System.out.println(sum);
    }
}
            

Output:

55

Method 2: Using Nested if-else Statements (Java)

public class Main {
    public static void main (String[] args) {
        int n = 10;
        System.out.println(n * (n + 1) / 2);
    }
}
            

Output:

55

Method 3: Using Recursion (Java)

public class Main {
    public static void main (String[] args) {
        int n = 10;
        int sum = getSum(n);
        System.out.println(sum);
    }
    static int getSum (int n) {
        if (n == 0)
            return 0;
        return n + getSum(n - 1);
    }
}
            

Output:

55

Explanation:

To calculate the sum recursively:

• Define a recursive function getSum() that calls itself.
• Base case: If n == 0, return 0.
• Otherwise, return n + getSum(n-1).
• Print the result.

While recursion simplifies the code, it has a time complexity of O(N) and uses extra memory due to function calls.