Kotlin recursive function: Sum of even numbers in a range

Kotlin Function: Exercise-13 with Solution

Write a Kotlin recursive function to calculate the sum of all even numbers in a range.

Sample Solution:

Kotlin Code:

fun sumEvenNumbers(start: Int, end: Int): Int {
    if (start > end) {
        return 0
    }
    
    return if (start % 2 == 0) {
        start + sumEvenNumbers(start + 2, end)
    } else {
        sumEvenNumbers(start + 1, end)
    }
}
 
 fun main() {
    val start = 10
    val end = 30
    val sum = sumEvenNumbers(start, end)
    println("Sum of even numbers from $start to $end: $sum")
}

Sample Output:

Sum of even numbers from 10 to 30: 220

Explanation:

In the above exercise -

• The function "sumEvenNumbers()" takes two parameters: start and end, representing the range of numbers to consider.
• In the base case, if start is greater than end, it means we have reached the end of the range, so we return 0.
• If start is an even number (start % 2 == 0), we add it to the sum of the remaining even numbers in the range. We recursively call the "sumEvenNumbers()" function with start + 2 to consider the next even number.
• If start is an odd number, we skip it and move to the next number by recursively calling the "sumEvenNumbers()" function with start + 1.
• The recursive calls continue until the base case is reached and the final sum is computed.

Kotlin Editor:

Previous: Binary tree as a binary search tree.
Next: Calculate factorial.