Kotlin Program to Check Armstrong Number

An Armstrong number, also known as a narcissistic number, is a number that is equal to the sum of its own digits each raised to the power of the number of digits. For example, 153 is an Armstrong number because 1^3 + 5^3 + 3^3 = 153. In this article, we will explore different Kotlin Program to Check Armstrong Number. We will cover three different solutions, each with an example, and explain the output for each.

Prerequisites

• Kotlin Installed: Ensure Kotlin is installed on your system. Download from Kotlin’s official website.
• IDE: Use an Integrated Development Environment (IDE) like IntelliJ IDEA or Android Studio for running Kotlin programs.
• Basic Understanding of Kotlin: Familiarity with basic Kotlin syntax and concepts.

1. Simple Method to Check Armstrong Number

Program

fun isArmstrong(number: Int): Boolean {
    var temp = number
    val numberOfDigits = number.toString().length
    var sum = 0

    while (temp > 0) {
        val digit = temp % 10
        sum += Math.pow(digit.toDouble(), numberOfDigits.toDouble()).toInt()
        temp /= 10
    }

    return sum == number
}

fun main() {
    val number = 153
    if (isArmstrong(number)) {
        println("$number is an Armstrong number.")
    } else {
        println("$number is not an Armstrong number.")
    }
}

1.2 Output

153 is an Armstrong number.

The isArmstrong function checks if 153 is an Armstrong number by calculating the sum of its digits raised to the power of the number of digits. The sum matches the original number.

2. Using String Conversion to Check Armstrong Number

Program

fun isArmstrongString(number: Int): Boolean {
    val digits = number.toString().map { it.toString().toInt() }
    val numberOfDigits = digits.size
    val sum = digits.map { Math.pow(it.toDouble(), numberOfDigits.toDouble()).toInt() }.sum()

    return sum == number
}

fun main() {
    val number = 370
    if (isArmstrongString(number)) {
        println("$number is an Armstrong number.")
    } else {
        println("$number is not an Armstrong number.")
    }
}

Output

370 is an Armstrong number.

The isArmstrongString function converts the number 370 to a string, processes each digit, and checks if the sum of the digits raised to the power of the number of digits equals the original number.

3. Using Recursion to Check Armstrong Number

Program

fun power(base: Int, exp: Int): Int {
    return if (exp == 0) 1 else base * power(base, exp - 1)
}

fun isArmstrongRecursive(number: Int, numberOfDigits: Int): Boolean {
    if (number == 0) return false
    var temp = number
    var sum = 0

    fun calculateSum(temp: Int): Int {
        return if (temp == 0) sum
        else {
            sum += power(temp % 10, numberOfDigits)
            calculateSum(temp / 10)
        }
    }

    val result = calculateSum(temp)
    return result == number
}

fun main() {
    val number = 9474
    val numberOfDigits = number.toString().length
    if (isArmstrongRecursive(number, numberOfDigits)) {
        println("$number is an Armstrong number.")
    } else {
        println("$number is not an Armstrong number.")
    }
}

3.2 Output

9474 is an Armstrong number.

The isArmstrongRecursive function uses recursion to check if 9474 is an Armstrong number by calculating the sum of its digits raised to the power of the number of digits and comparing it with the original number.

Conclusion

Checking if a number is an Armstrong number can be done using different methods. The simple method involves basic iteration and modulus operations. The string conversion method leverages Kotlin’s string manipulation capabilities for simplicity. The recursive method offers a more functional approach. Each method has its own advantages and can be chosen based on the specific requirements and preferences.