Coding Challenge Of The Day

[Corporal Agarn]

Tried to leave a similar message earlier but CP locked. I was going to add this is not QA. :)

[jesarg]

private int ToInt(string rom)
{
int length = rom.Length;
int result = 0;
for(int loop1=0; loop1 < length; loop1++)
{
char current = rom[loop1];
char next = loop1 < length - 1 ? rom[loop1 + 1] : ' ';
switch(current)
{
case 'I':
result += next == 'V' || next == 'X' ? -1 : 1;
break;
case 'V':
result += 5;
break;
case 'X':
result += next == 'L' || next == 'C' ? -10 : 10;
break;
case 'L':
result += 50;
break;
case 'C':
result += next == 'D' || next == 'M' ? -100 : 100;
break;
case 'D':
result += 500;
break;
case 'M':
result += 1000;
break;
}
}
return result;
}

[Lost User]

Or, somewhat more tersely,

def r2d3(r,(s,M,C,X,I,z,V,L,D)=["%%s%d"%v for v in[1001,1000,100,10,1,0,5,50,500]]):
return eval("".join([
p%"+-"[eval( p%"%s>"%d%"")]
for d,p in zip(map(eval,'%sz'%r),map(eval,'s%s'%r))
][1:]))

[Luc Pattyn]

that would be where most Romans are, don't you think? :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

[Luc Pattyn]

no arrays, no dictionaries, no obscure language, just some original coding:

public static bool TryParseRoman(string wellFormedRoman, out int val) {
val=0;
int prevDigit=0;
foreach (char c in wellFormedRoman) {
int index="IVXLCDM".IndexOf(c);
if (index<0) {val=0; return false;}
int digit=1;
int factor=5;
while (--index>=0) { digit*=factor; factor=7-factor; }
if (prevDigit

BTW: is it Friday already?

:)

Luc Pattyn [My Articles] Nil Volentibus Arduum

[PIEBALDconsult]

I'm unsure when I wrote this, but it must have been the 90s, in VAX C or DEC C. I'm shocked (shocked! I say) at the inconsistent braces. :wtf:

size_t
roman2dec
(
char *subject
)
{
size_t result = 0 , current , high = 0 ;
int index ;

for ( index = strlen(subject)-1 ; index >= 0 ; index-- ) {
    switch ( (char) \*(subject + index) )
    {
        case 'I' :
        case 'i' : current =    1 ; break ;

        case 'V' :
        case 'v' : current =    5 ; break ;

        case 'X' :
        case 'x' : current =   10 ; break ;

        case 'L' :
        case 'l' : current =   50 ; break ;

        case 'C' :
        case 'c' : current =  100 ; break ;

        case 'D' :
        case 'd' : current =  500 ; break ;

        case 'M' :
        case 'm' : current = 1000 ; break ;

        default  : current =    0 ; break ;
    }

    if ( current < high )
        result -= current ;
    else
    {
       result += current ;
       high = current ;
    }
}

return ( result ) ;

}

[PIEBALDconsult]

That's dreadful. :wtf:

[PIEBALDconsult]

Seems a waste of RAM.

[arcosupportus]

did you get here number?

[jsc42]

Apologies if other respondents have used a similar technique, but I have deliberately not looked at the other replies before attempting this challenge so that I am not influenced by other people's ideas. The following is in JavaScript, not obfuscated. The tricks are: Using an object literal as a lookup table and treating the double chars as subtractors from the second single chars (e.g. CM = [CM] + [M] = -100 + 1000 = 900). The only awkward part is preventing the last char being counted twice - once as a single char and once as a double char with no second char (this is done by appending '?').

// Roman to Arabic character translations
function RtoA(r) // r is roman numerals in any case
{
// Roman to Arabic conversion table
var Rch =
{
// Single chars: Add each value separately to the total
I: 1, V: 5, X: 10, L: 50, C: 100, D: 500, M: 1000,
// Double chars: Modify the sum of the second char as subtractors
CM: -100, CD: -100, XC: -10, XL: -10, IX: -1, IV: -1
};

var	R   = r.toUpperCase();  // Ignore case
var	A   = 0;    // Arabic equivalent

// Parse the text converting valid single chars and double chars
// Set any invalid single or double char combinations as translating to zero
for (var i = 0; i < R.length; i++)
{
	var	ch	= R.charAt(i);
	A	+= 
		Rch\[ch + (R.charAt(i + 1) || '?')\]	// Double char conversion
		||	Rch\[ch\]	// Single char conversion
		||	0;	// No conversion - invalid char
};	// for

return	A;

}

alert(RtoA('MDC')); // 1600
alert(RtoA('mcmxcix')); // 1999

[RobertHarris]

First time post so hope this looks OK; 1 CRT "NUMERALS: ": ; INPUT NUM 2 CRT "NUMBER : ":ICONV(NUM, 'NR') 3 END Written in UniVerse BASIC.

[yiangos]

Or, somewhere in between:

def a6(roman):
if len(roman)==0:
return 0
mapping={"I":1,"V":5,"X":10,"L":50,"C":100,"D":500,"M":1000}
values=[mapping[digit] for digit in roman.upper()]
for i in range(len(values)):
if i

also, added capitalization tolerance, so that "MCM" and "mcm" evaluate the same. I haven't added a check that the argument is a valid roman numeral, but that is left as an exercise to the reader ;P

Φευ! Εδόμεθα υπό ρηννοσχήμων λύκων!
(Alas! We're devoured by lamb-guised wolves!)

[Pascal Ganaye]

I hope it will be obscure enough. ;)

class Program
class Program
{
static int RomanToArabic(string r)
{
int x, y, z = x = y = 0;
foreach (char c in r)
y += ((z = (int)Math.Pow(10, (z = "ivxlcdm".IndexOf((char)(c | ' '))) / 2) * (1 + 4 * (z & 1))) > x ? -2 * x + (x = z) : x = z);
return y;
}

    static void Main(string\[\] args)
    {
        Console.WriteLine(RomanToArabic("MDC"));	// 1600
        Console.WriteLine(RomanToArabic("mcmxcix"));	// 1999
        Console.ReadKey();
    }
    
}

}

[Pascal Ganaye]

This is definitely better than my attempt.

[Luc Pattyn]

Nice. I like the % ' ' bits, and appreciate you used literal VII. :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

[Pascal Ganaye]

oops I removed the % ' '... Ok I put back a:

"ivxlcdm".IndexOf((char)(c | ' '))

[Pascal Ganaye]

This is my final answer

static int RomanToArabic(string roman, int x = 0, int y=0)
{
return roman.Length == 0 ? 0 : (y = (int)Math.Pow(10, (y = "ivxlcdm".IndexOf((char)(roman[0] | ' '))) / 2) * (1 + 4 * (y & 1))) + (y > x ? -2 * x : 0) + RomanToArabic(roman.Substring(1), y);
}

[Alan Balkany]

Geez, I thought it was going to be something hard.

"Microsoft -- Adding unnecessary complexity to your work since 1987!"

[Reese Currie]

OK, I admit it isn't very small. Scala is number 46 on the Tiobe Index this month, so perhaps it is obscure enough to qualify. Being a "functional" language there are actually 3 functions but I nested them in one.

def convertRomanToArabic(romanNumeral: String): Int = {
  
  var previous = 0
  
  def convertSingleRomanNumeral(numeral: Char): Int = {
    numeral match {
      case 'I' => 1
      case 'V' => 5
      case 'X' => 10
      case 'L' => 50
      case 'C' => 100
      case 'D' => 500
      case 'M' => 1000
    }
  }
  
  def addRomans(next: Int, accumulator: Int): Int = {
    if (previous == 0) previous = accumulator
    var addto = if (previous > next) next \* -1 else next
    previous = next
    accumulator + addto
  }
  
  val values = romanNumeral.toList.map(n => convertSingleRomanNumeral(n))
  values.reduceRight(addRomans)
}

[AnonimityPreferred]

FUNCTION Roman2Dec(cRoman)

LOCAL nPointer := len(cRoman)  
LOCAL nPos := 0,nFaceVal := 0,nLastVal := 0, nReturn := 0

WHILE nPointer > 0
    nPos     := at(substr(cRoman, nPointer, 1),'IVXLCDM') -1 
    nFaceVal := (10 ^ int((nPos)/2)) \* (1+((nPos) % 2 \* 4))
    nReturn  += iif(nFaceVal < nLastVal, -nFaceVal, nFaceVal)
    IF nFaceVal > nLastVal
        nLastVal := nFaceVal
    ENDIF
    nPointer--    
ENDDO

RETURN nReturn