# Integer to Roman in C

Given a decimal number n, we have to convert this into Roman numeral. The value n lies in the range 1 to 4000. These are some Roman Numerals.

Number
Numeral
1
I
4
IV
5
V
9
IX
10
X
40
XL
50
L
90
XC
100
C
400
CD
500
D
900
CM
1000
M
4000
MMMM

So if the number n = 859, its Roman Numeral will be DCCCLIX

To solve this, we will follow these steps

• Define an array to store numeral and corresponding values for the given list. That is called nume array
• we are using a recursive approach, the function decToRom() is used. this is taking nume array and the number num.
• The decToRom() will be like
• if num is not 0, then
• max := find maximum value from nume array that is not larger than num
• append the value for that max into the result string
• num := num – max value
• decToRom(nume, num)

## Example

Let us see the following implementation to get a better understanding −

#include<stdio.h>
typedef struct{
char *sym;
int val;
}numeral;
int maxNume(numeral *nu, int num){
int i, index;
for(i = 0; i<15; i++){//15 numerals in array
if(nu[i].val <= num)
index = i;
}
//gretest value numeral index, not greater than number
return index;
}
void decToRoman(numeral *nu, int num){
int max;
if(num != 0){
max = maxNume(nu, num);
printf("%s", nu[max].sym);
num -= nu[max].val;//decrease number
decToRoman(nu, num);//recursively print numerals
}
}
main(){
int number;
numeral nume[15] = {{"I",1},{"IV",4},{"V",5},{"IX",9}, {"X",10},{"XL",40},{"L",50},{"XC",90},
{"C",100},{"CD",400},{"D",500},{"CM",900},{"M",1000},{"MMMM",4000},{"V'",5000}};
printf("Enter a decimal number: ");
scanf("%d", &number);
if(number >0 && number <= 5000){//checking input number
printf("The Roman equivalent of %d is ", number);
decToRoman(nume, number);
}
else{
printf("Invalid Input");
}
printf("");
}

## Input

570
3574

## Output

DLXX
MMMDLXXIV