"Hexadecimal Numbers"

In computers, everything is represented in 1s and 0s which is called a binary number.

There are numerous ways of representing any regular (decimal) number. One of those ways is called hexadecimal representation. This system uses the digits 0 thru 9 in addition to the letters A B C D E F (which represent 10 thru 15 respectively).

Given an input file of 500 decimal numbers (decimalsB.txt), how many times IN TOTAL does the letter D appear when each number is converted into hexadecimal format?

Note: This is NOT the same file as Problem 20.

The same as challenge 20 except this time convert to hex and remove everything that isn't D.

Awnser:

Source:

include(MISC.'fn.fetch.php'); 

function solution(){
   $result = 0;
   $list = fetch('http://www.cstutoringcenter.com/problems/files/decimalsB.txt');
   $lines = explode("\n", $list);
   foreach($lines as $decno) {
      	  // convert decimal to hex and remove everything except D
      $hexno = preg_replace('/[^D\-\._]/si' , '' , dechex($decno)); 
      $result += strlen($hexno); // length of $hexno = no of D's
   }
   echo "= ".$result."";
}