PHP Program to Count set bits in an integer
Last Updated :
02 Jan, 2019
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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
Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.
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!
