PHP Challenges: Reverse the bits of an integer (32 bits unsigned)

Last update on December 20 2024 10:28:26 (UTC/GMT +8 hours)

Write a PHP program to reverse the bits of an integer (32 bits unsigned).

Input : 1234

For example, 1234 represented in binary as 10011010010 and returns 1260388352 which represents in binary as 1001011001000000000000000000000.

Explanation :

PHP: Reverse the bits of an integer (32 bits unsigned)

Sample Solution :

PHP Code :

<?php
// Function to reverse the bits of an integer
function reverse_integer($n)
{
    // Initialize a variable to store the reversed integer
    $result = 0;
    
    // Loop through 32 bits (assuming integers are represented by 32 bits)
    for ($i = 0; $i < 32; $i++)
    {
        // Shift the result to the left by 1 bit
        $result <<= 1;
        
        // OR operation to set the least significant bit of result with the least significant bit of n
        $result |= ($n & 1);
        
        // Shift n to the right by 1 bit
        $n >>= 1;
    }
    
    // Return the reversed integer
    return $result;
}   

// Test the reverse_integer function with input 1234 and print the result
print_r(reverse_integer(1234) . "\n");
?>

Explanation:

Here is a brief explanation of the above PHP code:

Function definition:

The code defines a function named "reverse_integer()" which reverses the bits of an integer. It takes a single parameter '$n', which is the integer whose bits are to be reversed.

Inside the function:

It initializes a variable '$result' to store the reversed integer.
It enters a "for" loop that iterates through 32 times, assuming integers are represented by 32 bits.
Within each iteration of the loop:

It shifts the bits of '$result' to the left by 1 position ($result <<= 1).
It performs a bitwise OR operation to set the least significant bit of '$result' with the least significant bit of '$n' ($result |= ($n & 1)).
It shifts the bits of '$n' to the right by 1 position ($n >>= 1).

After the loop, it returns the reversed integer stored in '$result'.

Function Call & Testing:

The "reverse_integer()" function is called with the input integer 1234.
Finally the "print_r()" function displays the reversed integer.

Sample Output:

1260388352

Flowchart:

PHP Code Editor:

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