Given a Roman numeral, the task is to find its corresponding decimal value.
Example :
Input: IX Output: 9 IX is a Roman symbol which represents 9 Input: XL Output: 40 XL is a Roman symbol which represents 40 Input: MCMIV Output: 1904 M is a thousand, CM is nine hundred and IV is four
Roman numerals are based on the following symbols.
SYMBOL VALUE 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
Approach: A number in Roman Numerals is a string of these symbols written in descending order(e.g. M’s first, followed by D’s, etc.). However, in a few specific cases, to avoid four characters being repeated in succession(such as IIII or XXXX), subtractive notation is often used as follows:
- I placed before V or X indicates one less, so four is IV (one less than 5) and 9 is IX (one less than 10).
- X placed before L or C indicates ten less, so forty is XL (10 less than 50) and 90 is XC (ten less than a hundred).
- C placed before D or M indicates a hundred less, so four hundred is CD (a hundred less than five hundred) and nine hundred is CM (a hundred less than a thousand).
Algorithm to convert Roman Numerals to Integer Number:
- Split the Roman Numeral string into Roman Symbols (character).
- Convert each symbol of Roman Numerals into the value it represents.
- Take symbol one by one from starting from index 0:
- If current value of symbol is greater than or equal to the value of next symbol, then add this value to the running total.
- else subtract this value by adding the value of next symbol to the running total.
Following is the implementation of the above algorithm:
C
// Program to convert Roman// Numerals to Numbers#include <stdio.h>#include <string.h>// This function returns value// of a Roman symbolint value(char r){ if (r == 'I') return 1; if (r == 'V') return 5; if (r == 'X') return 10; if (r == 'L') return 50; if (r == 'C') return 100; if (r == 'D') return 500; if (r == 'M') return 1000; return -1;}// Returns decimal value of// roman numaralint romanToDecimal(char str[]){ // Initialize result int res = 0; // Traverse given input for (int i = 0; i < strlen(str); i++) { // Getting value of symbol s[i] int s1 = value(str[i]); if (i + 1 < strlen(str)) { // Getting value of symbol s[i+1] int s2 = value(str[i + 1]); // Comparing both values if (s1 >= s2) { // Value of current symbol // is greater or equal to // the next symbol res = res + s1; } else { // Value of current symbol is // less than the next symbol res = res + s2 - s1; i++; } } else { res = res + s1; } } return res;}// Driver Codeint main(){ // Considering inputs given are valid char str[10] = "MCMIV"; printf("Integer form of Roman Numeral is %d",romanToDecimal(str)); return 0;} |
C++
// Program to convert Roman// Numerals to Numbers#include <bits/stdc++.h>using namespace std;// This function returns value// of a Roman symbolint value(char r){ if (r == 'I') return 1; if (r == 'V') return 5; if (r == 'X') return 10; if (r == 'L') return 50; if (r == 'C') return 100; if (r == 'D') return 500; if (r == 'M') return 1000; return -1;}// Returns decimal value of// roman numaralint romanToDecimal(string& str){ // Initialize result int res = 0; // Traverse given input for (int i = 0; i < str.length(); i++) { // Getting value of symbol s[i] int s1 = value(str[i]); if (i + 1 < str.length()) { // Getting value of symbol s[i+1] int s2 = value(str[i + 1]); // Comparing both values if (s1 >= s2) { // Value of current symbol // is greater or equal to // the next symbol res = res + s1; } else { // Value of current symbol is // less than the next symbol res = res + s2 - s1; i++; } } else { res = res + s1; } } return res;}// Driver Codeint main(){ // Considering inputs given are valid string str = "MCMIV"; cout << "Integer form of Roman Numeral is " << romanToDecimal(str) << endl; return 0;} |
Java
// Program to convert Roman// Numerals to Numbersimport java.util.*;public class RomanToNumber { // This function returns // value of a Roman symbol int value(char r) { if (r == 'I') return 1; if (r == 'V') return 5; if (r == 'X') return 10; if (r == 'L') return 50; if (r == 'C') return 100; if (r == 'D') return 500; if (r == 'M') return 1000; return -1; } // Finds decimal value of a // given roman numeral int romanToDecimal(String str) { // Initialize result int res = 0; for (int i = 0; i < str.length(); i++) { // Getting value of symbol s[i] int s1 = value(str.charAt(i)); // Getting value of symbol s[i+1] if (i + 1 < str.length()) { int s2 = value(str.charAt(i + 1)); // Comparing both values if (s1 >= s2) { // Value of current symbol // is greater or equalto // the next symbol res = res + s1; } else { // Value of current symbol is // less than the next symbol res = res + s2 - s1; i++; } } else { res = res + s1; } } return res; } // Driver Code public static void main(String args[]) { RomanToNumber ob = new RomanToNumber(); // Considering inputs given are valid String str = "MCMIV"; System.out.println("Integer form of Roman Numeral" + " is " + ob.romanToDecimal(str)); }} |
Python
# Python program to convert Roman Numerals# to Numbers# This function returns value of each Roman symboldef value(r): if (r == 'I'): return 1 if (r == 'V'): return 5 if (r == 'X'): return 10 if (r == 'L'): return 50 if (r == 'C'): return 100 if (r == 'D'): return 500 if (r == 'M'): return 1000 return -1def romanToDecimal(str): res = 0 i = 0 while (i < len(str)): # Getting value of symbol s[i] s1 = value(str[i]) if (i + 1 < len(str)): # Getting value of symbol s[i + 1] s2 = value(str[i + 1]) # Comparing both values if (s1 >= s2): # Value of current symbol is greater # or equal to the next symbol res = res + s1 i = i + 1 else: # Value of current symbol is greater # or equal to the next symbol res = res + s2 - s1 i = i + 2 else: res = res + s1 i = i + 1 return res# Driver codeprint("Integer form of Roman Numeral is"),print(romanToDecimal("MCMIV")) |
C#
// C# Program to convert Roman// Numerals to Numbersusing System;class GFG { // This function returns value // of a Roman symbol public virtual int value(char r) { if (r == 'I') return 1; if (r == 'V') return 5; if (r == 'X') return 10; if (r == 'L') return 50; if (r == 'C') return 100; if (r == 'D') return 500; if (r == 'M') return 1000; return -1; } // Finds decimal value of a // given roman numeral public virtual int romanToDecimal(string str) { // Initialize result int res = 0; for (int i = 0; i < str.Length; i++) { // Getting value of symbol s[i] int s1 = value(str[i]); // Getting value of symbol s[i+1] if (i + 1 < str.Length) { int s2 = value(str[i + 1]); // Comparing both values if (s1 >= s2) { // Value of current symbol is greater // or equalto the next symbol res = res + s1; } else { res = res + s2 - s1; i++; // Value of current symbol is // less than the next symbol } } else { res = res + s1; i++; } } return res; } // Driver Code public static void Main(string[] args) { GFG ob = new GFG(); // Considering inputs given are valid string str = "MCMIV"; Console.WriteLine("Integer form of Roman Numeral" + " is " + ob.romanToDecimal(str)); }}// This code is contributed by Shrikant13 |
PHP
<?php// Program to convert Roman// Numerals to Numbers// This function returns // value of a Roman symbolfunction value($r){ if ($r == 'I') return 1; if ($r == 'V') return 5; if ($r == 'X') return 10; if ($r == 'L') return 50; if ($r == 'C') return 100; if ($r == 'D') return 500; if ($r == 'M') return 1000; return -1;}// Returns decimal value// of roman numeralfunction romanToDecimal(&$str){ // Initialize result $res = 0; // Traverse given input for ($i = 0; $i < strlen($str); $i++) { // Getting value of // symbol s[i] $s1 = value($str[$i]); if ($i+1 < strlen($str)) { // Getting value of // symbol s[i+1] $s2 = value($str[$i + 1]); // Comparing both values if ($s1 >= $s2) { // Value of current symbol // is greater or equal to // the next symbol $res = $res + $s1; } else { $res = $res + $s2 - $s1; $i++; // Value of current symbol is // less than the next symbol } } else { $res = $res + $s1; $i++; } } return $res;}// Driver Code// Considering inputs// given are valid$str ="MCMIV";echo "Integer form of Roman Numeral is ", romanToDecimal($str), "\n";// This code is contributed by ajit?> |
Javascript
<script>// Program to convert Roman// Numerals to Numberspublic // This function returns // value of a Roman symbol function value(r) { if (r == 'I') return 1; if (r == 'V') return 5; if (r == 'X') return 10; if (r == 'L') return 50; if (r == 'C') return 100; if (r == 'D') return 500; if (r == 'M') return 1000; return -1; } // Finds decimal value of a // given roman numeral function romanToDecimal( str) { // Initialize result var res = 0; for (i = 0; i < str.length; i++) { // Getting value of symbol s[i] var s1 = value(str.charAt(i)); // Getting value of symbol s[i+1] if (i + 1 < str.length) { var s2 = value(str.charAt(i + 1)); // Comparing both values if (s1 >= s2) { // Value of current symbol // is greater or equalto // the next symbol res = res + s1; } else { // Value of current symbol is // less than the next symbol res = res + s2 - s1; i++; } } else { res = res + s1; } } return res; } // Driver Code // Considering inputs given are valid var str = "MCMIV"; document.write("Integer form of Roman Numeral" + " is " + romanToDecimal(str));// This code is contributed by umadevi9616</script> |
Output
Integer form of Roman Numeral is 1904
Complexity Analysis:
- Time Complexity: O(n), where n is the length of the string.
Only one traversal of the string is required. - Space Complexity: O(1).
As no extra space is required.
Another solution –
C++
// Program to convert Roman// Numerals to Numbers#include <bits/stdc++.h>using namespace std;// This function returns value// of a Roman symbolint romanToDecimal(string& str){ map<char, int> m; m.insert({ 'I', 1 }); m.insert({ 'V', 5 }); m.insert({ 'X', 10 }); m.insert({ 'L', 50 }); m.insert({ 'C', 100 }); m.insert({ 'D', 500 }); m.insert({ 'M', 1000 }); int sum = 0; for (int i = 0; i < str.length(); i++) { /*If present value is less than next value, subtract present from next value and add the resultant to the sum variable.*/ if (m[str[i]] < m[str[i + 1]]) { sum+=m[str[i+1]]-m[str[i]]; i++; continue; } sum += m[str[i]]; } return sum;}// Driver Codeint main(){ // Considering inputs given are valid string str = "MCMIV"; cout << "Integer form of Roman Numeral is " << romanToDecimal(str) << endl; return 0;} |
Java
// Program to convert Roman// Numerals to Numbersimport java.util.Map;import java.util.HashMap;class GFG{ private static final Map<Character, Integer> roman = new HashMap<Character, Integer>() {{ put('I', 1); put('V', 5); put('X', 10); put('L', 50); put('C', 100); put('D', 500); put('M', 1000);}};// This function returns value// of a Roman symbolprivate static int romanToInt(String s){ int sum = 0; int n = s.length(); for(int i = 0; i < n; i++) { // If present value is less than next value, // subtract present from next value and add the // resultant to the sum variable. if (i != n - 1 && roman.get(s.charAt(i)) < roman.get(s.charAt(i + 1))) { sum += roman.get(s.charAt(i + 1)) - roman.get(s.charAt(i)); i++; } else { sum += roman.get(s.charAt(i)); } } return sum;}// Driver Codepublic static void main(String[] args) { // Considering inputs given are valid String input = "MCMIV"; System.out.print("Integer form of Roman Numeral is " + romanToInt(input));}}// This code is contributed by rahuldevgarg |
Python3
# Program to convert Roman# Numerals to Numbersroman = {}roman['I'] = 1roman['V'] = 5roman['X'] = 10roman['L'] = 50roman['C'] = 100roman['D'] = 500roman['M'] = 1000 # This function returns value# of a Roman symboldef romanToInt(s): sum = 0 n = len(s) i = 0 while i < n : # If present value is less than next value, # subtract present from next value and add the # resultant to the sum variable. # print(roman[s[i]],roman[s[i+1]]) if (i != n - 1 and roman[s[i]] < roman[s[i + 1]]): sum += roman[s[i + 1]] - roman[s[i]] i += 2 continue else: sum += roman[s[i]] i += 1 return sum# Driver Code # Considering inputs given are validinput = "MCMIV"print(f"Integer form of Roman Numeral is {romanToInt(input)}")# This code is contributed by shinjanpatra |
C#
// Program to convert Roman// Numerals to Numbersusing System;using System.Collections.Generic;public class GFG { static Dictionary<char, int> roman = new Dictionary<char, int>(); // This function returns value // of a Roman symbol public static int romanToInt(String s) { int sum = 0; int n = s.Length; for (int i = 0; i < n; i++) { // If present value is less than next value, // subtract present from next value and add the // resultant to the sum variable. if (i != n - 1 && roman[s[i]] < roman[s[i + 1]]) { sum += roman[s[i + 1]] - roman[s[i]]; i++; } else { sum += roman[s[i]]; } } return sum; } // Driver Code public static void Main(String[] args) { roman['I'] = 1; roman['V'] =5; roman['X'] =10; roman['L'] =50; roman['C'] =100; roman['D'] =500; roman['M'] =1000; // Considering inputs given are valid String input = "MCMIV"; Console.Write("int form of Roman Numeral is " + romanToInt(input)); }}// This code is contributed by Rajput-Ji |
Javascript
<script>// Program to convert Roman// Numerals to Numbers var roman = new Map() ; roman.set('I', 1); roman.set('V', 5); roman.set('X', 10); roman.set('L', 50); roman.set('C', 100); roman.set('D', 500); roman.set('M', 1000); // This function returns value // of a Roman symbol function romanToInt( s) { var sum = 0; var n = s.length; for (i = 0; i < n; i++) { // If present value is less than next value, // subtract present from next value and add the // resultant to the sum variable. if (i != n - 1 && roman.get(s.charAt(i)) < roman.get(s.charAt(i + 1))) { sum += roman.get(s.charAt(i + 1)) - roman.get(s.charAt(i)); i++; } else { sum += roman.get(s.charAt(i)); } } return sum; } // Driver Code // Considering inputs given are valid var input = "MCMIV"; document.write("Integer form of Roman Numeral is " + romanToInt(input));// This code is contributed by Rajput-Ji</script> |
Output
Integer form of Roman Numeral is 1904
Time complexity – O(N)
Auxiliary Space – O(1)
Another Solution: Shorter code using python
C++
#include <iostream>#include <unordered_map>int romanToInt(std::string s) { std::unordered_map<char, int> translations = { {'I', 1}, {'V', 5}, {'X', 10}, {'L', 50}, {'C', 100}, {'D', 500}, {'M', 1000} }; int number = 0; s = s + ' '; for (int i = 0; i < s.size() - 1; i++) { if (translations[s[i]] < translations[s[i+1]]) { number -= translations[s[i]]; } else { number += translations[s[i]]; } } return number;}int main() { std::cout << romanToInt("MCMIV") << std::endl; return 0;} |
Java
// Java Program to convert Roman// Numerals to Numbersimport java.io.*;import java.util.*;class GFG { public static void romanToInt(String s) { Map<Character,Integer> translations=new HashMap<Character,Integer>(); //Adding elements to map translations.put('I',1); translations.put('V',5); translations.put('X',10); translations.put('L',50); translations.put('C',100); translations.put('D',500); translations.put('M',1000); s = s.replace("IV","IIII"); s = s.replace("IX","VIIII"); s = s.replace("XL","XXXX"); s = s.replace("XC","LXXXX"); s = s.replace("CD","CCCC"); s = s.replace("CM","DCCCC"); int number = 0; for (int i = 0; i < s.length(); i++) { number = number + (translations.get(s.charAt(i))); } System.out.println(number); } public static void main (String[] args) { romanToInt("MCMIV"); }}// This code is contributed by kothavvsaakash |
C#
// C# Program to convert Roman// Numerals to Numbersusing System;using System.Collections.Generic;using System.Collections;public class GFG { public static void romanToInt(String s) { var translations = new Dictionary<char, int>(); // Adding elements to map translations['I'] = 1; translations['V'] = 5; translations['X'] = 10; translations['L'] = 50; translations['C'] = 100; translations['D'] = 500; translations['M'] = 1000; s = s.Replace("IV", "IIII"); s = s.Replace("IX", "VIIII"); s = s.Replace("XL", "XXXX"); s = s.Replace("XC", "LXXXX"); s = s.Replace("CD", "CCCC"); s = s.Replace("CM", "DCCCC"); var number = 0; for (int i = 0; i < s.Length; i++) { number = number + (translations[s[i]]); } Console.WriteLine(number); } public static void Main(String[] args) { romanToInt("MCMIV"); }}// This code is contributed by Aarti_Rathi |
Python3
def romanToInt(s): translations = { "I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000 } number = 0 s = s.replace("IV", "IIII").replace("IX", "VIIII") s = s.replace("XL", "XXXX").replace("XC", "LXXXX") s = s.replace("CD", "CCCC").replace("CM", "DCCCC") for char in s: number += translations[char] print(number) romanToInt('MCMIV') |
Javascript
<script>function romanToInt(s){ let translations = new Map() translations.set("I",1) translations.set("V",5) translations.set("X",10) translations.set("L",50) translations.set("C",100) translations.set("D",500) translations.set("M",1000) let number = 0 s = s.replace("IV", "IIII").replace("IX", "VIIII") s = s.replace("XL", "XXXX").replace("XC", "LXXXX") s = s.replace("CD", "CCCC").replace("CM", "DCCCC") for(let char of s) number += translations.get(char) document.write(number)} romanToInt('MCMIV')// code is contributed by shinjanpatra</script> |
Output
1904
Time complexity – O(N)
Auxiliary Space – O(1)
Roman to integer using Ladder If-Else approach :
This approach basically follows the fundamental logic of roman numbers, applying the condition in ladder form like if the first character is ‘I’ then the next should be ‘V’ to make it 4 in number else it will be 1.
Implementation of the approach:
C++
// Program to convert Roman// Numerals to Numbers#include <bits/stdc++.h>using namespace std;int romanToDecimal(string s){ // declare two variables first // will calculate the number // and second will help // in iterating through the // string character-wise int ans = 0, i; for (i = 0; i < s.size() - 1; i++) { if (s[i] == 'I' && s[i + 1] == 'V') { ans += 4; i++; continue; } else if (s[i] == 'I' && s[i + 1] == 'X') { ans += 9; i++; continue; } else if (s[i] == 'X' && s[i + 1] == 'L') { ans += 40; i++; continue; } else if (s[i] == 'X' && s[i + 1] == 'C') { ans += 90; i++; continue; } else if (s[i] == 'C' && s[i + 1] == 'D') { ans += 400; i++; continue; } else if (s[i] == 'C' && s[i + 1] == 'M') { ans += 900; i++; continue; } // till this we checked all the category like // 4,9,40,90 etc. else if (s[i] == 'I') ans += 1; else if (s[i] == 'V') ans += 5; else if (s[i] == 'X') ans += 10; else if (s[i] == 'L') ans += 50; else if (s[i] == 'C') ans += 100; else if (s[i] == 'D') ans += 500; else if (s[i] == 'M') ans += 1000; } // for last character that // left in the string if last // two char comes not in // the category of 4,9,40,90 etc // as loop is iterating till size-1*/ if (s.size() > i) { if (s[i] == 'I') ans += 1; else if (s[i] == 'V') ans += 5; else if (s[i] == 'X') ans += 10; else if (s[i] == 'L') ans += 50; else if (s[i] == 'C') ans += 100; else if (s[i] == 'D') ans += 500; else if (s[i] == 'M') ans += 1000; } return ans;}// Driver Codeint main(){ // Considering inputs given are valid string str = "MCMIV"; cout << "Integer form of Roman Numeral is " << romanToDecimal(str) << endl; return 0;} |
C
// C Program to convert// Roman number to integer#include <stdio.h>#include <string.h>int romanToDecimal(char* s){ // declare two variables first // will calculate the number // and second will help // in iterating through the // string character-wise*/ int ans = 0, i; for (i = 0; s[i] != '\0'; i++) { if (s[i] == 'I' && s[i + 1] == 'V') { ans += 4; i++; continue; } else if (s[i] == 'I' && s[i + 1] == 'X') { ans += 9; i++; continue; } else if (s[i] == 'X' && s[i + 1] == 'L') { ans += 40; i++; continue; } else if (s[i] == 'X' && s[i + 1] == 'C') { ans += 90; i++; continue; } else if (s[i] == 'C' && s[i + 1] == 'D') { ans += 400; i++; continue; } else if (s[i] == 'C' && s[i + 1] == 'M') { ans += 900; i++; continue; } // till this we checked all the category like // 4,9,40,90 etc. else if (s[i] == 'I') ans += 1; else if (s[i] == 'V') ans += 5; else if (s[i] == 'X') ans += 10; else if (s[i] == 'L') ans += 50; else if (s[i] == 'C') ans += 100; else if (s[i] == 'D') ans += 500; else if (s[i] == 'M') ans += 1000; } // for last character that // left in the string if last // two char comes not in the // category of 4,9,40,90 etc // as loop is iterating till size-1*/ if (s[i] != '\0') { if (s[i] == 'I') ans += 1; else if (s[i] == 'V') ans += 5; else if (s[i] == 'X') ans += 10; else if (s[i] == 'L') ans += 50; else if (s[i] == 'C') ans += 100; else if (s[i] == 'D') ans += 500; else if (s[i] == 'M') ans += 1000; } return ans;}int main(){ // Considering inputs given are valid char str[] = "MCMIV"; printf("Integer form of Roman Numeral is %d\n", romanToDecimal(str)); return 0;} |
Python3
def romanToDecimal(s: str) -> int: # declare two variables first # will calculate the number # and second will help # in iterating through the # string character-wise ans = 0 i = 0 while i < len(s) - 1: if s[i] == 'I' and s[i + 1] == 'V': ans += 4 i += 2 elif s[i] == 'I' and s[i + 1] == 'X': ans += 9 i += 2 elif s[i] == 'X' and s[i + 1] == 'L': ans += 40 i += 2 elif s[i] == 'X' and s[i + 1] == 'C': ans += 90 i += 2 elif s[i] == 'C' and s[i + 1] == 'D': ans += 400 i += 2 elif s[i] == 'C' and s[i + 1] == 'M': ans += 900 i += 2 # till this we checked all the category like # 4,9,40,90 etc. else: if s[i] == 'I': ans += 1 elif s[i] == 'V': ans += 5 elif s[i] == 'X': ans += 10 elif s[i] == 'L': ans += 50 elif s[i] == 'C': ans += 100 elif s[i] == 'D': ans += 500 elif s[i] == 'M': ans += 1000 i += 1 # for last character that # left in the string if last # two char comes not in # the category of 4,9,40,90 etc # as loop is iterating till size-1 if i < len(s): if s[i] == 'I': ans += 1 elif s[i] == 'V': ans += 5 elif s[i] == 'X': ans += 10 elif s[i] == 'L': ans += 50 elif s[i] == 'C': ans += 100 elif s[i] == 'D': ans += 500 elif s[i] == 'M': ans += 1000 return ans# Driver Codeif __name__ == "__main__": # Considering inputs given are valid str = "MCMIV" print("Integer form of Roman Numeral is", romanToDecimal(str)) |
C#
// C# code addition using System;class Program{ static int RomanToDecimal(string s) { // declare two variables first // will calculate the number // and second will help // in iterating through the // string character-wise*/ int ans = 0; for (int i = 0; i < s.Length - 1; i++) { if (s[i] == 'I' && s[i + 1] == 'V') { ans += -1; i++; continue; } else if (s[i] == 'I' && s[i + 1] == 'X') { ans += 9; i++; continue; } else if (s[i] == 'X' && s[i + 1] == 'L') { ans += 40; i++; continue; } else if (s[i] == 'X' && s[i + 1] == 'C') { ans += 90; i++; continue; } else if (s[i] == 'C' && s[i + 1] == 'D') { ans += 400; i++; continue; } else if (s[i] == 'C' && s[i + 1] == 'M') { ans += 900; i++; continue; } // till this we checked all the category like // 4,9,40,90 etc. else if (s[i] == 'I') ans += 1; else if (s[i] == 'V') ans += 5; else if (s[i] == 'X') ans += 10; else if (s[i] == 'L') ans += 50; else if (s[i] == 'C') ans += 100; else if (s[i] == 'D') ans += 500; else if (s[i] == 'M') ans += 1000; } // for last character that // left in the string if last // two char comes not in // the category of 4,9,40,90 etc // as loop is iterating till size-1 if (s.Length > 0) { int lastCharIndex = s.Length - 1; if (s[lastCharIndex] == 'I') ans += 1; else if (s[lastCharIndex] == 'V') ans += 5; else if (s[lastCharIndex] == 'X') ans += 10; else if (s[lastCharIndex] == 'L') ans += 50; else if (s[lastCharIndex] == 'C') ans += 100; else if (s[lastCharIndex] == 'D') ans += 500; else if (s[lastCharIndex] == 'M') ans += 1000; } return ans; } static void Main(string[] args) { // Considering inputs given are valid string str = "MCMIV"; Console.WriteLine("Integer form of Roman Numeral is {0}", RomanToDecimal(str)); }}// The code is contributed by Nidhi goel. |
Javascript
// Program to convert Roman// Numerals to Numbersfunction romanToDecimal(s){ // declare two variables first // will calculate the number // and second will help // in iterating through the // string character-wise let ans = 0, i=0; for (i = 0; i < s.length - 1; i++) { if (s[i] === 'I' && s[i + 1] === 'V') { ans += 4; i++; continue; } else if (s[i] === 'I' && s[i + 1] === 'X') { ans += 9; i++; continue; } else if (s[i] === 'X' && s[i + 1] === 'L') { ans += 40; i++; continue; } else if (s[i] === 'X' && s[i + 1] === 'C') { ans += 90; i++; continue; } else if (s[i] === 'C' && s[i + 1] === 'D') { ans += 400; i++; continue; } else if (s[i] === 'C' && s[i + 1] === 'M') { ans += 900; i++; continue; } // till this we checked all the category like // 4,9,40,90 etc. else if (s[i] === 'I') ans += 1; else if (s[i] === 'V') ans += 5; else if (s[i] === 'X') ans += 10; else if (s[i] === 'L') ans += 50; else if (s[i] === 'C') ans += 100; else if (s[i] === 'D') ans += 500; else if (s[i] === 'M') ans += 1000; } // for last character that // left in the string if last // two char comes not in // the category of 4,9,40,90 etc // as loop is iterating till size-1*/ if (s.length > i) { if (s[i] === 'I') ans += 1; else if (s[i] === 'V') ans += 5; else if (s[i] === 'X') ans += 10; else if (s[i] === 'L') ans += 50; else if (s[i] === 'C') ans += 100; else if (s[i] === 'D') ans += 500; else if (s[i] === 'M') ans += 1000; } return ans;}// Considering inputs given are validlet str = "MCMIV";console.log("Integer form of Roman Numeral is " + romanToDecimal(str)); |
Java
import java.util.*;public class RomanToDecimal { public static int romanToDecimal(String s) { // Declare a map to store the values of Roman numerals Map<Character, Integer> map = new HashMap<>(); map.put('I', 1); map.put('V', 5); map.put('X', 10); map.put('L', 50); map.put('C', 100); map.put('D', 500); map.put('M', 1000); int ans = 0; // Iterate through the string character-wise for (int i = 0; i < s.length(); i++) { // If the current character is smaller than the next character, subtract its value from the answer if (i < s.length() - 1 && map.get(s.charAt(i)) < map.get(s.charAt(i + 1))) { ans -= map.get(s.charAt(i)); } // Else, add its value to the answer else { ans += map.get(s.charAt(i)); } } return ans; } // Driver code public static void main(String[] args) { // Considering inputs given are valid String str = "MCMIV"; System.out.println("Integer form of Roman Numeral is " + romanToDecimal(str)); }} |
Output
Integer form of Roman Numeral is 1904
Time complexity – O(N)
Auxiliary Space – O(1)
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