C Program to check if a Number Is Positive Or Negative Even or Odd

Check if a Number is Even or Odd in C

Given an integer input, the objective is to write a code to Check if a Number is Even or Odd in C Language.

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

C Program to Find the Sum of First N Natural Numbers

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: Iterative Approach

This method uses a loop to add numbers from 1 to N iteratively.

#include <stdio.h>
int main() {
    int n, sum = 0;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)
        sum += i;
    printf("Sum is %d", sum);
    return 0;
}
            

Output:

5
Sum is 15

Method 2: Using Formula

The mathematical formula for the sum of first N natural numbers is: Sum = N * (N + 1) / 2.

#include <stdio.h>
int main() {
    int n;
    scanf("%d", &n);
    int sum = n * (n + 1) / 2;
    printf("The sum is %d", sum);
    return 0;
}
            

Output:

6
The sum is 21

Method 3: Recursive Approach

Recursion is used to break the problem into smaller subproblems, reducing the number by 1 in each step.

#include <stdio.h>
int getSum(int sum, int n) {
    if(n == 0) return sum;
    return n + getSum(sum, n - 1);
}
int main() {
    int n, sum = 0;
    scanf("%d", &n);
    printf("%d", getSum(sum, n));
    return 0;
}
            

Output:

5
Sum is 15