Integer to Roman

Given an integer, convert it to a roman numeral.

Input is guaranteed to be within the range from 1 to 3999.

     string intToRoman(int num) {
         string res;
         char a[]={'I','X','C','M'};
         char b[]={'V','L','D'};
         int i=,ld=,n=;
         while(i>=)
         {
             ld=num/n;
             num%=n;
             n/=;

             switch(ld)
             {
                 case :break;
                 case :{res+=a[i];break;}
                 case :{res=res+a[i]+a[i];break;}
                 case :{res=res+a[i]+a[i]+a[i];break;}
                 case :{res=res+a[i]+b[i];break;}
                 case :{res=res+b[i];break;}
                 case :{res=res+b[i]+a[i];break;}
                 case :{res=res+b[i]+a[i]+a[i];break;}
                 case :{res=res+b[i]+a[i]+a[i]+a[i];break;}
                 case :{res=res+a[i]+a[i+];break;}
                 default :break;

             }
             i--;

         }
         return res;

     }