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# Another C string conversion question

Posted on 1997-10-22
Medium Priority
268 Views
You have provided me with the answer to my last question->
How to convert integers to roman numerals (ie input: 25 output: 25 = XXV), but how do I the reverse? (ie input: XXV output: XXV = 25)

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Question by:trying
[X]
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LVL 3

Expert Comment

ID: 1255924
It looks like your homework. eh?

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LVL 1

Expert Comment

ID: 1255925
50 points ? You skinflint.
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Author Comment

ID: 1255926
If you can't answer the question, then just say so. But I will increase the number of points to 100, as an added incentive.
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LVL 10

Accepted Solution

RONSLOW earned 400 total points
ID: 1255927
char ch;
int thousands = 0;
int fivehundreds = 0;
int hundreds = 0;
int fities = 0;
int tens = 0;
int fives = 0;
int ones = 0;
int total = 0;
while ((ch = getc(stdin)) != EOF) {
ch = toupper(ch);
switch (ch) {
case 'M': thousands+=1000; break;
case 'D': if (hundreds>0) hundreds = -hundreds; fivehundreds+=500; break;
case 'C': hundreds+=100; break;
case 'L': if (tens>0) tens = -tens; fifties+=50; break;
case 'X': tens+=10; break;
case 'V': if (ones>0) ones = -ones; fives+=5; break;
case 'I': ones+=1; break;
}
}
total = thousands+fivehundreds+hundreds+fifties+tens+fives+ones;

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LVL 84

Expert Comment

ID: 1255928
MCMXCIX
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LVL 10

Expert Comment

ID: 1255929
Oops

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LVL 10

Expert Comment

ID: 1255930
Try this then...

switch (ch) {
case 'M': if (hundreds>0) hundreds = -hundreds; thousands+=1000; break;
case 'D': if (hundreds>0) hundreds = -hundreds; fivehundreds+=500; break;
case 'C': if (tens>0) tens = -tens; hundreds+=100; break;
case 'L': if (tens>0) tens = -tens; fifties+=50; break;
case 'X': if (ones>0) ones = -ones; tens+=10; break;
case 'V': if (ones>0) ones = -ones; fives+=5; break;
case 'I': ones+=1; break;
}

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LVL 84

Expert Comment

ID: 1255931
I've been trying to find a definitive ruling on whether
IC or VL or CMCM are legal roman numerals,
but I have been unable to find anything either forbiding or permitting them.
Does anyone know for sure, or can anyone cite a reference?
Some sources, while not saying whether thise forms are legal,
do give explicit rules for evaluating roman numerals,
which if applied to those forms give different results from the above code.
0

LVL 10

Expert Comment

ID: 1255932
Try this then...

switch (ch) {
case 'M': if (fivehundreds>0) fivehundreds = -fivehundreds;
case 'D': if (hundreds>0) hundreds = -hundreds;
case 'C': if (fifties>0) fifties = -fifties;
case 'L': if (tens>0) tens = -tens;
case 'X': if (fives>0) fives = -fives;
case 'V': if (ones>0) ones = -ones;
}
switch (ch) {
case 'M': thousands+=1000; break;
case 'D': fivehundreds+=500; break;
case 'C': hundreds+=100; break;
case 'L': fifties+=50; break;
case 'X': tens+=10; break;
case 'V': fives+=5; break;
case 'I': ones+=1; break;
}

0

LVL 84

Expert Comment

ID: 1255933
That last comment wan't meant to criticize the code,
(which should work to reverse anything a reasonable interger to roman conversion would produce)
so much as to ask about exactly what stings are valid as roman numerals.
Is IXC a roman numeral?
BTW, IVIX, (if it's a roman numeral) would be 13 by every source I can find.
But I can't find a source the tells me whether or not it is a roman numeral.
0

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