Online PHP editor | refs for colSe

<?php function reduce($bits, $value = '0') { if (strlen($bits) == 1) { // a single bit can be flipped as needed return ($bits[0] == $value) ? 0 : 1; } if ($bits[0] == $value) { // nothing to do with this bit, flip the remainder return reduce(substr($bits, 1)); } // need to convert balance of string to 1 followed by 0's // then we can flip this bit, and then reduce the new string to 0 return reduce(substr($bits, 1), '1') + 1 + reduce(str_pad('1', strlen($bits) - 1, '0')); } for ($i = 0; $i < 128; $i++) { echo "$i (" . decbin($i) . ") takes " . reduce(decbin($i)) . " steps\n"; }