C program to convert Roman number to decimal number



C code for roman numbers to English numbers

#include<stdio.h>
#include<string.h>

int digitValue(char);

int main(){

    char roman_Number[1000];
    int i=0;
    long int number =0;
   
    printf("Enter any roman number (Valid digits are I, V, X, L, C, D, M):  \n");
    scanf("%s",roman_Number);
   
    while(roman_Number[i]){
        
         if(digitValue(roman_Number[i]) < 0){
             printf("Invalid roman digit : %c",roman_Number[i]);
             return 0;
         }
            
         if((strlen(roman_Number) -i) > 2){
             if(digitValue(roman_Number[i]) < digitValue(roman_Number[i+2])){
                 printf("Invalid roman number");
                 return 0;
             }
         }

         if(digitValue(roman_Number[i]) >= digitValue(roman_Number[i+1]))
             number = number + digitValue(roman_Number[i]);
         else{
             number = number + (digitValue(roman_Number[i+1]) - digitValue(roman_Number[i]));
             i++;
         }
         i++;
    }
        
    printf("Its decimal value is : %ld",number);
   
    return 0;

}

int digitValue(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 '\0': value = 0; break;
         default: value = -1; 
    }

    return value;
}

Sample output:

Enter any roman number (Valid digits are I, V, X, L, C, D, M):
XVII
Its decimal value is: 17


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10 comments:

Unknown said...

pls give some description of this program.

7/16/13, 9:07 AM
Srikanth Chindam said...
This comment has been removed by the author.
12/23/14, 8:15 AM
Srikanth Chindam said...
This comment has been removed by the author.
12/23/14, 8:17 AM
fedillah koh said...

Using c language, the input and output are 0 and 1. Its output is identical to the input in the even position but inverted in the odd position. For example, input 0000111 it output 1010010. How to do this ?

4/12/15, 5:50 PM
Srikanth Chindam said...

Check This Code
may be it is simpler than your code

#include
#include
int main()
{
int a[10],len,i,j,val;
char rom[20];
printf("Enter the Roman Numeral:");
scanf("%s",rom);
printf("%s",rom);
i=0;
while(rom[i]!='\0')
{
if(rom[i]=='I')
a[i]=1;
else if(rom[i]=='V')
a[i]=5;
else if(rom[i]=='X')
a[i]=10;
else if(rom[i]=='L')
a[i]=50;
else if(rom[i]=='C')
a[i]=100;
else if(rom[i]=='D')
a[i]=500;
else if(rom[i]=='M')
a[i]=1000;
printf("\n %d %d",a[i],i);
i++;
}

len=strlen(rom);
printf("\n %d\n",len);
for(i=len-1;i>=0;i--)
{
if(i!=0)
{
if(a[i]>a[i-1])
a[i-1]=a[i]-a[i-1];
else
val=val+a[i];
}
else
val=val+a[i];
}
printf("Its Decimal Equivalent is: %d",val);
return 0;
}

8/2/15, 5:57 PM
Unknown said...

Could you explain this part for me?
if(digitValue(roman_Number[i]) >= digitValue(roman_Number[i+1]))
number = number + digitValue(roman_Number[i]);
else{
number = number + (digitValue(roman_Number[i+1]) - digitValue(roman_Number[i]));
i++;
}
i++;
}

10/17/15, 8:35 PM
Unknown said...

This is probably the shortest/simplest solution to this problem

#include < stdio.h >

void main(){
char ROMAN[][3] = { "M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I" };
int NUM[] = { 1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1 };
char result[20] = { 0 };
int num, i;

printf("Enter a Number: ");
scanf("%i", &num);
printf("\nRoman Numeral.: ");
for(i = 0; num > 0 && num < 3999; i++)
while(num/NUM[i]){
printf("%s", ROMAN[i]);
num -= NUM[i];
}
getchar();
}

10/29/15, 6:36 AM
tahuhu said...

is it possible to have one that starts with
int romanToInt(char *s){
...
//and ends with
...
return -1;
} /* romanToInt */

12/3/15, 4:45 AM
tahuhu said...

is it possible to have one that starts with
int romanToInt(char *s){
...
//and ends with
...
return -1;
} /* romanToInt */

12/3/15, 4:45 AM
Unknown said...

#include
int main()
{
int n,a=1;
printf("entetr the num.");

do
{
scanf("%d",&n);
while(n>=1000 || n>=900)
{
if(n>=1000)
printf("M",n=n-1000);
else if(n>=900)
printf("CM",n=n-900);
}
while(n>=500 || n>=400)
{
if(n>=500)
printf("D",n=n-500);
else if(n>=400)
printf("CD",n=n-400);
}
while(n>=100 || n>=90)
{
if(n>=100)
printf("C",n=n-100);
else if(n>=40)
printf("XC",n=n-40);
}
while(n>=50 || n>=40)
{
if(n>=50)
printf("L",n=n-50);
else if(n>=40)
printf("XL",n=n-40);
}
while(n>=10 || n>=9)
{
if(n>=10)
printf("X",n=n-10);
else if(n>=9)
printf("IX",n=n-9);
}
while(n>=5 || n>=4)
{
if(n>=5)
printf("V",n=n-5);
else if(n>=4)
printf("IV",n=n-4);
}
while(n>=1)
printf("I",n=n-1);
scanf("%d",&a);
}
while(a!=0);
return 0;
}

2/18/17, 12:18 AM

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