Check if a Number is an Armstrong Number in PHP

Armstrong Number

Armstrong number is a number in which the sum of its digits raised to the power of the number of digits is equal to the number itself. In this article, we are going to discuss how we can check if a given number is Armstrong number or not.

Examples

Let's understand Armstrong's Number with the help of some input-output examples.

Input

9474

Output

Yes

Explanation

This is a four digit-number. The digit in this number are 9, 4, 7 and 4.

9474 = 94 + 44 + 74 + 44
= 6561 + 256 + 2401 + 256
= 9474

So, this is an Armstrong number.

Input

153

Output

Yes

Explanation

This is a 3-digit number. The digits in this number are 1, 5, and 3.

153 = 13 + 53 + 33
= 1 + 125 + 27
=153

So, this is an Armstrong number.

Solution Approach

We will take an integer as input. We first write a function to count the total number of digit in the number. Now we initialize a variable to store the sum and store original number in any variable. Now, we extract each digit of the number using modulo operator and add the digit raised to the power of total number of digit. Finally we check if the sum calculated is equal to original number.

Implementation in PHP

Follow the below steps to implement the solution of the above problem in PHP -

• We write a function to count the number of digits in a number.
• Now, write another function to check if a number is an Armstrong number or not.
• Initialize a variable sum and store the original number
• Now extract each digit of the number using the modulo operator one by one and add the digit raised to the power of count of digit.
• Drop the last digit using the division operator.
• After coming out of the loop, check if the sum is equal to the original number.
• If yes then this is an Armstrong number.

Example

Following is the implementation in PHP following the above discussed implementation steps.

<?php
// Function to count the number of digits in a number
function countDigits($num) {
return strlen((string)$num);
}

// Function to check if a number is an Armstrong number
function isArmstrong($num) {
$k = countDigits($num); 
$sum = 0; 
$originalNum = $num;

while ($num > 0) {
$ld = $num % 10; 
$sum += pow($ld, $k); 
$num = (int)($num / 10); 
}

return $sum == $originalNum;
}


$number = 153; 

if (isArmstrong($number)) {
echo "$number is an Armstrong number.";
} else {
echo "$number is not an Armstrong number.";
}
?>

Output

153 is an Armstrong number.

Time Complexity: O(d * n), where d is the number of digits and n is the raised power on each digit
Space Complexity: O(1), constant space