Question

How to round a number to the nearest power of 2 in PHP

Answer 1

/**
 * Rounds an integer to the nearest power of 2.
 *
 * return int The nearest power of 2
 */
function roundToNearestPowerOf2(int $n): int {
    if ($n <= 0) {
        return 0;
    }

    $prevPower = 1;
    while ($prevPower << 1 <= $n) {
        $prevPower <<= 1;
    }

    $nextPower = $prevPower << 1;

    return ($n - $prevPower < $nextPower - $n) ? $prevPower : $nextPower;
}

$num = 37;

echo "Nearest power of 2: " . roundToNearestPowerOf2($num) . PHP_EOL;


/*
run:

Nearest power of 2: 32

*/

 

70+ SQL courses for beginners and professionals

Answer 2

function roundToNearestPowerOf2(int $n): int {
    if ($n <= 0) {
        return 0;
    }

    // Compute the previous power of 2 using bit length
    $prevPower = 1 << (int)floor(log($n, 2));

    // Compute the next power of 2
    $nextPower = $prevPower << 1;

    // Return the one closest to n
    return ($n - $prevPower < $nextPower - $n) ? $prevPower : $nextPower;
}

$num = 37;

echo "Nearest power of 2: " . roundToNearestPowerOf2($num) . PHP_EOL;



/*
run:

Nearest power of 2: 32

*/

 

70+ SQL courses for beginners and professionals