PHP Challenges: Find the single element appears once in an array where every element appears twice except for one

Last update on June 03 2025 13:00:11 (UTC/GMT +8 hours)

Write a PHP program to find the single element appears once in an array where every element appears twice except for one.

Input : array(5, 3, 0, 3, 0, 5, 7, 7, 9)

Sample Solution :

PHP Code :

<?php
// Function to find the single number in an array using bitwise XOR operation
function single_number($arr)
{
    // Initialize the result variable
    $result = 0;

    // Iterate through the array
    for ($i = 0; $i < sizeof($arr); $i++)
    {
        // Use bitwise XOR operation to find the single number
        $result = $result ^ $arr[$i];
    }

    // Return the single number found
    return $result;
}

// Define an array of numbers
$num = array(5, 3, 0, 3, 0, 5, 7, 7, 9);

// Print the single number found in the array
print_r(single_number($num) . "\n");
?>

Explanation:

Here is a brief explanation of the above PHP code:

Function definition:

The code defines a function named "single_number()" which finds the single number in an array using a bitwise XOR operation. It takes an array '$arr' as input.

Inside the function:

It initializes the variable '$result' to 0.
It iterates through the array using a "for" loop.
Within each iteration, it performs a bitwise XOR operation between '$result' and the current element of the array.
After iterating through the array, the variable '$result' holds the single number as a result of XORing all the elements.

Function Call & Testing:

An array '$num' is defined as a set of numbers.
The "single_number()" function is called with this array as input.
The single number found is printed using "print_r()".

Sample Output:

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