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Rooted by: BinaryGap
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  • Fundamentals
    Logic
    Code 
    // > given a positive integer N
// do not have to account for N of 0

function binaryGap($n) 
{
  return preg_match_all('/1(0+)1/', decbin($n), $matches) ? max(array_map('strlen', $matches[1])) : 0;
}
     Test Cases 
    <?php
use PHPUnit\Framework\TestCase;

// PHPUnit Test Examples:
// TODO: Replace examples and use TDD by writing your own tests
class ExampleTest extends TestCase
{
    // test function names should start with "test"
    public function testThatSomethingShouldHappen() {
      $this->assertEquals(5, binaryGap(1041));
      $this->assertEquals(2, binaryGap(9));
      $this->assertEquals(0, binaryGap(15));
    }
}
    View Run Output
  • Code
    • // > given a positive integer N
    • // do not have to account for N of 0
    • function binaryGap($n)
    • {
    • while (!($n & 1))
    • {
    • $n >>= 1;
    • }
    • $n >>= 1;
    • $max = 0;
    • $current = 0;
    • while ($n)
    • {
    • if ($n & 1)
    • {
    • $max = max($max, $current);
    • $current = 0;
    • }
    • else
    • {
    • ++$current;
    • }
    • $n >>= 1;
    • }
    • return $max;
    • }
    • return preg_match_all('/1(0+)1/', decbin($n), $matches) ? max(array_map('strlen', $matches[1])) : 0;
    • }