Traversing and Summing Even Digits in Kotlin

Welcome to another exciting session! In today's lesson, we face a unique coding challenge using Kotlin. We will traverse the digits of a number using a while loop and a specific condition. You will hone your skills in working with loops and conditional statements, both of which are fundamental building blocks of programming in Kotlin. Shall we begin?

Our mission today is somewhat mind-twisting! We need to create a function that operates on an input integer to calculate the sum of its even-numbered digits. However, we won't convert this integer to a String at any point during this process. For example, given an integer n with a value of 4625, our output should be 12, which is the sum of the even digits 4, 6, and 2.

Remember, n will always be a positive integer that falls within the range from 1 to 100,000,000. Are you ready for the challenge? Awesome! Let's get started!

We begin by setting up the basic structure for our function. In this step, we define a variable, digitSum, that will accumulate the sum of the even digits.

Here's the initial framework of our function:

fun solution(n: Int): Int {
    var digitSum = 0
    // The function expands from here.
}

The most effective tool for iterating through the digits of n is a while loop. The loop will run as long as n is greater than zero. Integrating this into our function produces:

fun solution(n: Int): Int {
    var digitSum = 0
    var number = n
    while (number > 0) {
        // Further development of the function will proceed here.
    }
}

Within our loop, we'll extract the last digit of number using the modulo operation (number % 10). If this digit is even, we add it to the digitSum.

After we process a digit, we'll truncate the last digit of number using integer division (number / 10). This step prepares the while loop for the next digit.

This is what the final code looks like:

fun solution(n: Int): Int {
    var digitSum = 0
    var number = n
    while (number > 0) {
        val digit = number % 10
        if (digit % 2 == 0) {  // Check if the digit is even.
            digitSum += digit
        }
        number /= 10  // Remove the last digit.
    }
    return digitSum
}

fun main() {
    val n = 4625
    println(solution(n))  // Output should be 12
}