PHP Program to Check if a Number is an Armstrong Number

Armstrong Number

The Armstrong number refers to the sum of n powers of each digit of a number equal to the number itself, where n is the number of digits of the number. This article will discuss how to check if a given number is an Armstrong number.

Example

Let's understand the Armstrong number with some input and output examples.

Enter

<code>9474</code>

Output

<code>是</code>

Explanation

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

<code>9474 = 9<sup>4</sup> + 4<sup>4</sup> + 7<sup>4</sup> + 4<sup>4</sup><br>= 6561 + 256 + 2401 + 256<br>= 9474</code>

So, this is an Armstrong number.

Enter

<code>153</code>

Output

<code>是</code>

Explanation

This is a triple digit. The numbers for this number are 1, 5 and 3.

<code>153 = 1<sup>3</sup> + 5<sup>3</sup> + 3<sup>3</sup><br>= 1 + 125 + 27<br>=153</code>

So, this is an Armstrong number.

Solution Method

We will get an integer as input. We first write a function to calculate the total number of digits. Now we initialize a variable to store the sum and store the original number in any variable. Now, we use the modulo operator to extract each number of numbers and add the power of numbers to the total number of digits. Finally, we check whether the calculated sum equals the original number.

PHP implementation

Access the solution to the above problem in PHP following the steps -

• We write a function to calculate the number of bits in a number.
• Now, write another function to check if a number is an Armstrong number.
• Initialize a variable sum and store the original number
• Now use the modulo operator to extract each number one by one and add the power of the number to the number count.
• Use the division operator to delete the last digit.
• After exiting the loop, check whether the sum is equal to the original number.
• If so, then this is an Armstrong number.

Example

The following is the implementation of the implementation steps discussed above in PHP.

<code class="language-php"><?php
// 计算数字位数的函数
function countDigits($num) {
    return strlen((string)$num);
}

// 检查数字是否为阿姆斯特朗数的函数
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 是阿姆斯特朗数。";
} else {
    echo "$number 不是阿姆斯特朗数。";
}
?></code>

Output

<code>153 是阿姆斯特朗数。</code>

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

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