Find Armstrong Numbers in an Interval in Go

In this tutorial, we will learn how to find all Armstrong numbers in a given interval in Go. We will cover the basic concept of Armstrong numbers and implement a function to identify Armstrong numbers within a specified range.

What is an 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 1³ + 5³ + 3³ = 153.

Syntax

The syntax to find Armstrong numbers in an interval in Go is:

import (
    "fmt"
    "math"
)

func isArmstrongNumber(num int) bool {
    originalNum := num
    var sum int
    numDigits := int(math.Log10(float64(num))) + 1

    for num != 0 {
        digit := num % 10
        sum += int(math.Pow(float64(digit), float64(numDigits)))
        num /= 10
    }

    return sum == originalNum
}

func findArmstrongNumbers(start, end int) []int {
    var armstrongNumbers []int
    for i := start; i <= end; i++ {
        if isArmstrongNumber(i) {
            armstrongNumbers = append(armstrongNumbers, i)
        }
    }
    return armstrongNumbers
}

Example 1: Finding Armstrong numbers in an interval

We can create a function to check if a number is an Armstrong number and use it to find all Armstrong numbers within a specified range.

For example,

  1. Import the fmt and math packages.
  2. Define a helper function named isArmstrongNumber that takes one parameter num of type int and returns a boolean indicating if num is an Armstrong number.
  3. Define a function named findArmstrongNumbers that takes two parameters start and end of type int.
  4. Initialize an empty slice to store the Armstrong numbers.
  5. Use a for loop to iterate from start to end (inclusive).
  6. For each number in the loop, check if it is an Armstrong number using the isArmstrongNumber function. If true, append it to the slice of Armstrong numbers.
  7. Return the slice of Armstrong numbers.
  8. In the main function, call the findArmstrongNumbers function with sample values and print the results.

Go Program

package main

import (
    "fmt"
    "math"
)

func isArmstrongNumber(num int) bool {
    originalNum := num
    var sum int
    numDigits := int(math.Log10(float64(num))) + 1

    for num != 0 {
        digit := num % 10
        sum += int(math.Pow(float64(digit), float64(numDigits)))
        num /= 10
    }

    return sum == originalNum
}

func findArmstrongNumbers(start, end int) []int {
    var armstrongNumbers []int
    for i := start; i <= end; i++ {
        if isArmstrongNumber(i) {
            armstrongNumbers = append(armstrongNumbers, i)
        }
    }
    return armstrongNumbers
}

func main() {
    // Define the interval
    start, end := 100, 9999

    // Find all Armstrong numbers in the interval
    armstrongNumbers := findArmstrongNumbers(start, end)
    fmt.Printf("Armstrong numbers between %d and %d are: %v\n", start, end, armstrongNumbers)
}

Output

Armstrong numbers between 100 and 9999 are: [153 370 371 407 1634 8208 9474]