How to Check if All Digits of Given Number are Same in PHP ?

Given a number, our task is to check if all the digits of a given number are the same. This can be useful in various scenarios, such as validating user input or processing numerical data. In this article, we will explore different approaches to check if a given number's digits are the same in PHP.

Examples:

Input: 1111
Output: All digits of 1111 are same
Input: 12345
Output: All digits of 12345 are not same

String Manipulation to Check if All Digits of Given Number are Same

One way to check if all digits are the same in a given integer is by first converting the number to a string. Then compare each characters of this string with the first one and return true if all the characters are same, otherwise false.

Example: Implementation of checking if all the digits of the given number are same in PHP using string concatenation.

<?php
// To check if all digits of given number are same
function areDigitsSame($number) {
    $numberStr = (string)$number;
    $firstDigit = $numberStr[0];
    for ($i = 1; $i < strlen($numberStr); $i++) {
        if ($numberStr[$i] != $firstDigit) {
            return false;
        }
    }
    return true;
}

// Given Number
$number = 1111;

if (areDigitsSame($number)) {
    echo "All digits of $number are same.";
} else {
    echo "All digits of $number are not same.";
}
?>

All digits of 1111 are same.

Time Complexity: O(d), where d is the number of digits in the given number.
Auxiliary Space: O(1)

Arithmetic Operations to Check if All Digits of Given Number are Same

Another approach to check if all digits are the same in a given integer is by comparing each digit directly by using arithmetic operations, without converting the number to a string.

Example: Implementation of checking if all the digits of the given number are same in PHP using arithmetic operations.

<?php
// To check if all digits of given number are same
function areDigitsSame($number) {
    $lastDigit = $number % 10;
    while ($number > 0) {
        $currentDigit = $number % 10;
        if ($currentDigit != $lastDigit) {
            return false;
        }
        $number = (int)($number / 10);
    }
    return true;
}

// Given Data
$number = 2222;

if (areDigitsSame($number)) {
    echo "All digits of $number are same.";
} else {
    echo "All digits of $number are not same.";
}
?>

All digits of 2222 are same.

Time Complexity: O(d), where d is the number of digits in the given number.
Auxiliary Space: O(1)

String Functions to Check if All Digits of Given Number are Same

PHP provides various methods to manipulate a string. We can use them to check if all the digits of a given string are same or not. First convert the number to a string and split it into an array of digits using str_split() function. Then use array_unique() function to remove duplicate digits and checks if the resulting array has only one element. If it does, all digits are the same; otherwise, they are not.

Example: Implementation of checking if all the digits of the given number are same in PHP using in-built string functions.

<?php
// To check if all digits of given number are same
function areDigitsSame($number) {
    $numberStr = (string)$number;
    return count(array_unique(str_split($numberStr))) === 1;
}

// Given Data
$number = 3333;

if (areDigitsSame($number)) {
    echo "All digits of $number are same.";
} else {
    echo "All digits of $number are not same.";
}
?>

All digits of 3333 are same.

Time Complexity: O(d), where d is the number of digits in the given number.
Auxiliary Space: O(1)

Using a Frequency Array

This approach involves creating an array to count the frequency of each digit (0-9). If only one digit has a non-zero frequency, then all digits in the number are the same.

Example: Implementation of checking if all the digits of the given number are the same in PHP using a frequency array.

<?php
// To check if all digits of given number are same
function areDigitsSame($number) {
    $frequency = array_fill(0, 10, 0);
    
    while ($number > 0) {
        $digit = $number % 10;
        $frequency[$digit]++;
        $number = (int)($number / 10);
    }
    
    $nonZeroCount = 0;
    foreach ($frequency as $count) {
        if ($count > 0) {
            $nonZeroCount++;
        }
    }
    
    return $nonZeroCount === 1;
}

// Given Data
$number = 4444;

if (areDigitsSame($number)) {
    echo "All digits of $number are same.";
} else {
    echo "All digits of $number are not same.";
}
?>

All digits of 4444 are same.

Using Regular Expressions

Another approach to check if all digits in a given number are the same is by using regular expressions. This method involves converting the number to a string and then using a regular expression pattern to determine if all characters in the string are identical.

Example: The following example demonstrates how to check if all the digits of a given number are the same using regular expressions in PHP.

<?php
function areAllDigitsSame($number) {
    // Convert the number to a string
    $numberStr = strval($number);

    // Use a regular expression to check if all characters are the same
    return preg_match('/^(\d)\1*$/', $numberStr) === 1;
}

$number1 = 1111;
$number2 = 12345;

if (areAllDigitsSame($number1)) {
    echo "All digits of $number1 are same\n"; 
} else {
    echo "All digits of $number1 are not same\n";
}

if (areAllDigitsSame($number2)) {
    echo "All digits of $number2 are same\n";
} else {
    echo "All digits of $number2 are not same\n"; 
}
?>

All digits of 1111 are same
All digits of 12345 are not same