Write a recursive function in C to find sum of all even or odd numbers in a given range. How to find sum of all even numbers between 1 to n using recursion in C programming.

**Example**

**Input**

Input lower limit: 1 Input upper limit: 100

**Output**

Sum of even numbers between 1 to 100 = 2550

## Required knowledge

Basic C programming, If else, Functions, Recursion

Must know – Program to find sum of even numbers using loop.

Finding sum of even or odd numbers in range is almost similar to previous program we did.

Learn more – Program to find sum of natural numbers using recursion.

## Declare recursive function to find sum of even number

- First give a meaningful name to our function, say
`sumOfEvenOdd()`

. - Next the function accepts two integer values from user i.e.
`start`and`end`range. Hence, update function declaration to`sumOfEvenOdd(int start, int end);`

. - Finally, after calculating sum of even or odd numbers the function must return it to the caller. Hence, return type of the function must be
`int`

.

Final function declaration to find sum of all even or odd numbers in given range is – `int sumOfEvenOdd(int start, int end);`

.

## Program to find sum of even or odd numbers using recursion

```
/**
* C program to find sum of all even or odd numbers in given range using recursion
*/
#include <stdio.h>
int sumOfEvenOdd(int start, int end);
int main()
{
int start, end, sum;
/* Input lower and upper limit from user */
printf("Enter lower limit: ");
scanf("%d", &start);
printf("Enter upper limit: ");
scanf("%d", &end);
printf("Sum of even/odd numbers between %d to %d = %d\n", start, end, sumOfEvenOdd(start, end));
return 0;
}
/**
* Find sum of all even or odd numbers recursively.
*/
int sumOfEvenOdd(int start, int end)
{
/* Base condition */
if(start > end)
return 0;
else
return (start + sumOfEvenOdd(start + 2, end));
}
```

Output

Enter lower limit: 2 Enter upper limit: 100 Sum of even/odd numbers between 2 to 100 = 2550

Happy coding ðŸ˜‰

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