gistfile1.aw

<?php
/*
Based on rules from http://en.wikipedia.org/wiki/Roman_numerals
*/
function romanToInt($roman){
	$int = 0;
	$characters = str_split($roman);
	$previous = null;
	$values = array('I' => 1, 'V' => 5, 'X' => 10, 'L' => 50, 'C' => 100, 'D' => 500, 'M' => 1000);
	foreach($characters as $character){
		// default of adding this characters value to current value
		$newValue = $int + $values[$character];
		
		// if the previous value is a "subtraction" case, we'll need to adjust accordingly
		if($previous == 'I' && in_array($character, array('V', 'X'))){
			// subtract 1, add adj value
			$newValue = ($int - 1) + $values[$character] - 1;
		}
		elseif($previous == 'X' && in_array($character, array('L', 'C'))){
			// subtract 10, add adj value
			$newValue = ($int - 10) + $values[$character] - 10;
		}
		elseif($previous == 'C' && in_array($character, array('D', 'M'))){
			// subtract 100, add adj value
			$newValue = ($int - 100) + $values[$character] - 100;
		}
		
		// set the new value and continue
		$int = $newValue;
		$previous = $character;
	}
	return $int;
}

/*

    to read from a file:

        $data = file('roman.txt');
        foreach($data as $line){ echo romanToInt($line); }
*/

// test it!
$inputs = array(
	'X',
	'C',
	'V',
	'I',
	'L',
	'D',
	'M',
	'IX',
	'III',
	'IV',
	'XC',
	'MM',
	'MDCCCCX',
	'MCMLIV',
	'MCMXC'
);

$answers = array(
	10,
	100,
	5,
	1,
	50,
	500,
	1000,
	9,
	3,
	4,
	90,
	2000,
	1910,
	1954,
	1990
);

for($i=0; $i<count($inputs); $i++){
	if(romanToInt($inputs[$i]) != $answers[$i]){
		print "Failed: ". $inputs[$i] ." != ". $answers[$i] ."; received ". romanToInt($inputs[$i]) ."\n";
	}
	else {
		print "Success! ". $inputs[$i] ." == ". $answers[$i] ."\n";
	}
}
?>