C++ converting base 10 to Roman numerals

[Bartholomew]

Oh, I didn't see you had posted--took me a while to do that translation. 1 moment.

Edit: Okay, you raise a valid point. I will think about how best to modify my method to do 9's, 90s, and 900s correctly. It will still be very short though.

 

[freemind]

Alright, let me have a shot at this:

#include <iostream>
#include <cstdio>

using namespace std;

int main(int argc, char **argv)         {
	int *input = new int();
	int *rom = new int[7];
	int *steps = new int[6];
	char *map = new char[7];
	*map = 'M'; *(map+1)='D'; *(map+2)='C'; *(map+3)='L'; *(map+4)='X';
	*(map+5)='V'; *(map+6)='I';

	printf("Please enter the number that must be converted: ");
	scanf("%i", input);
	
	*rom = *input / 1000;
	*(rom + 1) = (*steps = *input % 1000) / 500;
	*(rom + 2) = (*(steps+1) = *steps % 500) / 100;
	*(rom + 3) = (*(steps+2) = *(steps+1) % 100) / 50;
	*(rom + 4) = (*(steps+3) = *(steps+2) % 50) / 10;
	*(rom + 5) = (*(steps+4) = *(steps+3) % 10) / 5;
	*(rom + 6) = (*(steps+4) % 5);
	
	printf("Here is your number in Roman numerals: ");
	for (register int i = 0; i < 6; i++) {
		for (register int k = 0; k < *(rom + i); k++) printf("%c", *(map + i));
	};

	switch(*(rom+6))	{
		case 1: printf("%s", "I"); break;
		case 2: printf("%s", "II"); break;
		case 3: printf("%s", "III"); break;
		case 4: printf("%s", "IV"); break;
		default: break;	};

	return 0;				}

Please compile Multi-threaded!

PS: Don't be hatin' on the printf!

 

[gnome]

Interesting, but not correct:

Please enter the number that must be converted: 1999
Here is your number in Roman numerals: MDCCCCLXXXXVIV

3 errors: DCCCC for 900, LXXXX for 90, VIV for 9


Edit: What's the "multithreaded" comment about?

 

[freemind]

Ah crap, didn't notice that. Awesome beta testing on your part.

I meant, if your compiler supports it (I think all compilers nowadays do), like gcc 3.4.x, compile it for Multi-threaded mode (to support Intel Hyper-Threading!) and notice the performance difference. I believe the code is significantly faster if it runs multithreaded.


Btw, I found this rather succint piece of code (I'm quite sure it works) http://home.att.net/~srschmitt/script_roman.html . I feel a JScript to C/C++ conversion is in order.

 

[gnome]

Btw, I found this rather succint piece of code (I'm quite sure it works) http://home.att.net/~srschmitt/script_roman.html . I feel a JScript to C/C++ conversion is in order.

That's no good -- it's not obfuscated at all!

Here's my latest effort. It's not as short as I'd hoped it would be, but I think it's cute:

#include <iostream>
#include <string>
#include <math.h>
using namespace std;         // added this line for MSVC 6.0
#define LTRS "MDCLXVI"
int iter[]={9,5,4};
void build(int& val, int p, string& s){
    int r = (int)pow(10,p);
    while(val>=r){
        val -= r;
    s += LTRS[6-2*p];
    }
}
void trim(string t, int i, int j, string &s){
    int ind = s.find(t,0);
    string tt;
    if (j!=1)
        tt += LTRS[2*i+2];
    j == 0 ? tt += LTRS[2*i] : tt += LTRS[2*i+1];
    if (ind >=0)
       s.replace(ind, iter[j], tt);
}
int main(){
    int i, j, k, p, dec;
        string t, roman;
    cout << "Enter integer to be translated:\n";
    cin >> dec;
    for(p = 3; p >=0; p--)
        build(dec, p, roman);
    for(i = 0; i < 3; i++) {
        for (j = 0; j < 3; j++) {
            t.erase();
            for(k = 0; k < iter[j]; k++)
                t += LTRS[2*i+2];
            trim(t,i,j,roman);
        }
    }
    cout << roman.c_str() << endl;            // edited for MSVC 6.0
    return 0;
}

 

[freemind]

I kinda half-understand your algorithm (it's very complex), but compiling it on Microsoft Visual C++ 7.0 and running in debug mode gives garbled output.
Did it give the correct lettering on your system?

P.S: AFAIK, the string class doesn't have operator overloading support for << (@ least not in the MSVC++ 7.0 implementation), which means 'cout << roman << endl;' threw tantrums. I had to change that to 'printf("%s", &roman);', but I doubt that's the cause of the messed result.

 

[gnome]

Sorry, it worked fine in my old Dev-C++ (mingw compiler).

It also works fine in with my g++ compiler, but for that one I had to add "using namespace std;" so I edited my previous post to add that line.

I also made a small change to that final cout so now it compiles and runs correctly in MSVC 6. I don't know about MSVC 7.

Funny thing is, I have MSVC7 (I think). A few months ago I bought a student copy of Visual Studio .net but never used it. So now I'm trying, and DAMN if I can't figure out how to compile ANYTHING with it. So far all I seem to have here is the world's most complicated editor. There's buttons for everything under the sun, but no "compile", no "build", no "run". How the heck do I get this thing to do something useful?

 

[freemind]

It works perfectly now!

I know what you mean. MSVC++.NET isn't exactly a quick-and-dirty superfast development IDE. But for large programs that use a lot of custom-built libraries, it is priceless. As for the compile, build and run buttons, it is quite silly that they don't exist in the default view. I simply use the shortcut Ctrl+Shift+B to build, and F5 to run (debug). Still, having used Borland C++ , Dev-C++ (it took forever to compile, I don't know why), and gcc/g++, I would still say that Microsoft makes the best compilers/IDEs around. Then again, I'm also known to be a M$-fanboy.

Kudos to gnome for a fine piece of code!

 

[Bartholomew]

Okay, here is my masterpiece!

#include <iostream>
int main(){
	string s = "IIIVIXXXLXCCCDCMMM";
	int n, c[] = {1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000};
	cin>>n;
	for(int i=12; i>-1;n%=c[i], i--)
		cout<<(n/c[i]>0?s.substr(i+(i+3)/4,i%4?(i-2)%4?2:1:n/c[i]):"");
}

Hopefully I translated this into C++ right; it does work in Java. If you can't get it to work I'll post the Java code which is a little longer.

 

[gnome]

Beautiful. I changed it slightly, adding "#include<string>", changed "String" to "string", and "cin >> n"; instead of your constant n.

#include <iostream>
#include <string>
int main(){
	string s = "IIIVIXXXLXCCCDCMMM";
	int n, c[] = {1, 4, 5, 9, 10, 40, 50, 90, 100, 400, 500, 900, 1000};
	cin >> n;
	for(int i=12; i>-1;n%=c[i], i--)
		cout<< (n/c[i]>0 ? s.substr(i+(i+3)/4, i%4 ? (i-2)%4 ? 2 : 1 : n/c[i]) : "");
}

edit: Oh, I see you already made two of those changes.

(But what if I have more than 3999 olives to count?)


I've never seen a compound conditional statement like that. Is is just composed from the inside out, i.e.:
n/c>0 ? ([/color] s.substr(i+(i+3)/4, [[/color] i%4 ? [ (i-2)%4 ? 2 : 1] : n/c ][/color] ) )[/color] : ""

 

[Bartholomew]

If you want to count more than 3999, you would use parentheses around letters as explained at http://mathworld.wolfram.com/RomanNumerals.html. You wouldn't write MMMM. 4000 would be written M(V)

Edit: Or you could add a vinculum by using 2 lines of output and an underscore.

If for some reason you want to use more than 3 M's, you can just add more M's at the end of string s.

Yes, that's how the conditional statement works.