Number to Roman Numerals

Data StructureMisc AlgorithmsAlgorithms

Roman numbers are non-positional numbers. Some numerals are placed together to form a number in roman numbers. For an example the number 75 can be expressed as 75 = 50 + 10 + 10 + 5, so the roman numerals are LXXV.

In this problem one number is provided in a decimal format, our task is to convert it into the Roman numeral strings.

There are different symbols and their value, like this.

I
IV
V
IX
X
XL
L
XC
C
CD
D
CM
M
MMMM
V’
1
4
5
9
10
40
50
90
100
400
500
900
1000
4000
5000


Using this table, we can easily find the roman numerals of a given number.

Input and Output

Input:
Decimal number: 3569
Output:
The Roman equivalent of 3569 is: MMMDLXIX

Algorithm

decToRoman(nuList, num)

Input: The numeral list with its value, number to convert into roman.

Output: The Roman numerals for the given number.

Begin
   if num ≠ 0, then
      max := get maximum numeral value, not greater than number
      display the nuList[max].symbol
      num := num – nuList[max].value
      decToRoman(nuList, num)
End

Example

#include<iostream>
using namespace std;

struct numeral {
   string sym;
   int val;
};

int maxNume(numeral nu[], int num) {
   int index;
   for(int 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);
      cout << nu[max].sym;
      num -= nu[max].val;   //decrease number
      decToRoman(nu, num);   //recursively print numerals
   }
}

int 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}
   };
   cout << "Enter a decimal number: "; cin >> number;

   if(number >0 && number <= 5000) {   //checking input number
      cout<<"The Roman equivalent of " << number<<" is: ";
         decToRoman(nume, number);
   }else {
      cout << "Invalid Input";
   }
}

Output

Enter a decimal number: 3569
The Roman equivalent of 3569 is: MMMDLXIX
raja
Published on 12-Jul-2018 11:52:06
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