Open In App

PHP Program to Count set bits in an integer

Last Updated : 02 Jan, 2019
Comments
Improve
Suggest changes
Like Article
Like
Report
Write an efficient program to count number of 1s in binary representation of an integer. Examples : 
Input : n = 6
Output : 2
Binary representation of 6 is 110 and has 2 set bits

Input : n = 13
Output : 3
Binary representation of 11 is 1101 and has 3 set bits
setbit 1. Simple Method Loop through all bits in an integer, check if a bit is set and if it is then increment the set bit count. See below program. PHP 
<?php
// Function to get no of set  
// bits in binary representation 
// of positive integer n 
function countSetBits($n)
{
    $count = 0;
    while ($n)
    {
        $count += $n & 1;
        $n >>= 1;
    }
    return $count;
}

// Driver Code
$i = 9;
echo countSetBits($i);

// This code is contributed by ajit
?>
Output: 
2
Recursive Approach : PHP 
<?php
// PHP implementation of recursive
// approach to find the number of 
// set bits in binary representation
// of positive integer n

// recursive function 
// to count set bits
function countSetBits($n)
{
    // base case
    if ($n == 0)
        return 0;

    else

        // if last bit set 
        // add 1 else add 0
        return ($n & 1) + 
                countSetBits($n >> 1);
}

// Driver code

// get value from user
$n = 9;

// function calling
echo countSetBits($n);

// This code is contributed by m_kit.
?>
Output: 
2
Please refer complete article on Count set bits in an integer for more details!

Next Article
How to find Sum the Digits of a given Number in PHP ?
author
kartik
Improve
Article Tags :

Similar Reads

We use cookies to ensure you have the best browsing experience on our website. By using our site, you acknowledge that you have read and understood our Cookie Policy & Privacy Policy
Lightbox