roman.c

#include <stdio.h>

#define l(x) ((((x)>='A')&&((x)<='Z'))?((x)-'A'):((x)-'a'))
#define a(x) (argc[1][(x)])
#define lv(x) (values[(x)])
#define before(x, a, b) (fcp[(x)-'a']=(a),scp[(x)-'a']=(b))
#define value(c, v) (values[(c)-'a']=(v))
int main(int argv, char **argc) {
    if (argv !=2) return puts("usage: ./roman 'MMXV'"),0;
    int result=0,nmf=0, count=0, c=0, max=0, cbbd=99999999;
    int fcp[26]={0}, scp[26]={0}, values[26]={0};

    /* FILL IN PRECEDENCE HERE */
    /* USE LOWERCASE */
    before('i', 'v', 'x'); // i can precede v or X
    before('x', 'l', 'c'); // x can precede l or c
    before('c', 'd', 'm'); // c can precede m or m

    /* FILL IN VALUE HERE */
    value('i', 1);
    value('v', 5);
    value('x', 10);
    value('l', 50);
    value('c', 100);
    value('d', 500);
    value('m', 1000);
    max = ('m');

    while(a(c)) {
        if(lv(l(a(c))) > cbbd)
            return printf("error invalid char: %c\n", a(c)), 1;
        int v = lv(l(a(c)));
        if(!a(c+1) || (v >= lv(l(a(c+1))))) result += (v);
        else if(((fcp[l(a(c))]==l(a(c+1))+'a')||(scp[l(a(c))]==l(a(c+1))+'a'))
                && (v < lv(l(a(c+1))))) {
            result += (lv(l(a(c+1))) - v);
            if(lv(l(a(c+1))) > cbbd)
                return printf("error invalid char: %c\n", a(c+1)), 1;
            cbbd=(cbbd>(v-1)?v-1:cbbd);
            if(c>0 && !fcp[l(a(c+1))] && l(argc[1][c-1]) == l(a(c+1)))
                return printf("bad sequence (%c%c%c)\n",a(c+1),a(c),a(c+1)),1;
            c++;
            if (nmf==l(a(c)))count--;
        }
        else return printf("error: %c before %c\n", a(c), a(c+1)), 1;
        if(nmf==l(a(c))) {
            if(l(a(c))!=l(max) && count == (fcp[l(a(c))]?3:1))
                return printf("too many ('%c':%i)\n",l(a(c))+'A',count+1),1;
        } else nmf=l(a(c)),count=0;
        if(a(c))c++;
        ++count,cbbd=cbbd>v?v:cbbd;
    }
    printf("%i\n", result);
}