Question

Problem Statement Create a program that will convert a decimal value into roman numeral, and output the result. The program will ask for an integer input, assume all inputs are valid, and the program should not end unless the user tells you to.

Refactoring Once your program is running correctly, put your conversion algorithm into a function named d_to_r(), which takes a string as parameter and return an int. You are allowed to create more helper functions if needed.

Link for Roman numerals: http://sierra.nmsu.edu/morandi/coursematerials/RomanNumerals.html

Answer 1

//I am little bit confused for your question as Refactoring Once your program is running correctly, put your conversion algorithm into a function named d_to_r(), which takes a string as parameter and return an int. SO i have provide roman to decimal also.

If any more reQuirement kindly ask.

PROGRAM

#include<stdio.h>
#include<stdlib.h>
int digit(char c);
void dtor(int num){
int decimal[] = {1000,900,500,400,100,90,50,40,10,9,5,4,1}; //base values
char *symbol[] = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"}; //roman symbols
int i = 0;

while(num){ //repeat process until num is not 0
while(num/decimal[i]){ //first base value that divides num is largest base value
printf("%s",symbol[i]); //print roman symbol equivalent to largest base value
num -= decimal[i]; //subtract largest base value from num
}
i++; //move to next base value to divide num
}
}
//METHOD to convert the roman numbers to decimal
//take argument as string and returns integer value
long int d_to_r(char roman_Number[1000])
{
int i=0;
long int number =0;
//loop to extract one by one characters from the string
while(roman_Number[i]){
//condition for invalid digit
if(digit(roman_Number[i]) < 0){
printf("Invalid roman digit : %c",roman_Number[i]);
return 0;
}
//condition for invalid roman number
if((strlen(roman_Number) -i) > 2){
if(digit(roman_Number[i]) < digit(roman_Number[i+2])){
printf("Invalid roman number");
return 0;
}
}
//condition to form the decimal numbers by using digit() method
if(digit(roman_Number[i]) >= digit(roman_Number[i+1]))
number = number + digit(roman_Number[i]);
else{
number = number + (digit(roman_Number[i+1]) - digit(roman_Number[i]));
i++;
}
i++;
}
//return the number
return number;

}

//method to set the decimal value for corresponding roman character
int digit(char c)
{
int value=0;
switch(c){
case 'I': value = 1; break;
case 'V': value = 5; break;
case 'X': value = 10; break;
case 'L': value = 50; break;
case 'C': value = 100; break;
case 'D': value = 500; break;
case 'M': value = 1000; break;
case '': value = 0; break;
default: value = -1;
}
//return the numeric value
return value;
}

int main()
{
   int n;
   char ch;
   char roman_Number[1000];
int i=0;
long int number =0;
//infinite loop for decimal to roman
   while(1)
   {
      printf(" Enter a decimal value");
      fflush(stdin);
      scanf("%d",&n);//ask for decimal value
      printf("%d = ",n);
      dtor(n);//call the method to display the roman equivalent
      //ask for further convertion to user
      printf(" Do you want to continue[Y/N]");
      fflush(stdin);
      scanf("%c",&ch);
      if(ch=='n' || ch=='N')
      break;
   }
   //infinite loop for roman to decimal
while(1)
   {
      //ask for roman value
   printf(" Enter any roman number (Valid digits are I, V, X, L, C, D, M): ");
   scanf("%s",roman_Number);
   //call the method to convert roman to decimal
       number=d_to_r(roman_Number);
       printf("Its decimal value is : %ld",number);
       //ask for further convertion to user
       printf(" Do you want to continue[Y/N]");
      fflush(stdin);
      scanf("%c",&ch);
      if(ch=='n' || ch=='N')
      break;
   }
}

OUTPUT