Roman To Integer Leetcode Javascript

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Introduction to the LeetCode platform and Roman to Integer problem


LeetCode is a popular platform where programmers can practice their coding skills by solving various problems. The platform has a vast collection of algorithmic problems that are designed to test a programmer’s understanding of data structures and algorithms.

One such problem is the Roman to Integer problem, which requires the conversion of a Roman numeral to its corresponding integer value. This problem is interesting because it requires understanding the rules of Roman numerals and also requires a good understanding of programming concepts such as loops and conditionals.

In the next sections, we will discuss the Roman to Integer problem in detail and learn how to solve it using JavaScript.

Understanding the Roman numerals system and conversions to integers

The Roman numeral system is a numeric system that originated in ancient Rome and was used throughout the Roman Empire. It uses letters from the Latin alphabet to represent values. The most common Roman numerals are:

  • I = 1
  • V = 5
  • X = 10
  • L = 50
  • C = 100
  • D = 500
  • M = 1000

Roman numerals are typically written largest to smallest from left to right. However, there are a few exceptions to this rule, for example:

  • IV = 4 (not IIII)
  • IX = 9 (not VIIII)
  • XL = 40 (not XXXX)
  • XC = 90 (not LXXXX)
  • CD = 400 (not CCCC)
  • CM = 900 (not DCCCC)

Converting Roman numerals to integers can be done by adding the numeric value of each Roman numeral symbol in left-to-right order. However, if a smaller value precedes a larger value, then the smaller value is subtracted from the larger value. For example, the Roman numeral ‘IV’ is 4 because ‘I’ comes before ‘V’ and so is subtracted from ‘V’.

In JavaScript, there are various algorithms and techniques for converting Roman numerals to integers. One such example is the ‘Roman to Integer’ problem on LeetCode, a popular coding platform. This problem involves writing a function that takes a Roman numeral string as input and returns the corresponding integer value.

Solving the Roman to Integer problem using JavaScript

When working on the Roman to Integer problem on LeetCode using JavaScript, there are several approaches that you can take to solve it. The problem requires you to convert a given Roman numeral to an integer.

One of the common approaches used for solving this problem involves creating a hash map to store the values of Roman numerals, then iterating over the Roman numeral string and checking the value of each character against its neighboring characters to determine the actual value. The algorithm then adds up the calculated values of each individual character to arrive at the final integer value.

Another approach involves using switch statements to check the value of each character and calculating its integer equivalent. This method is more efficient than using the hash map because it requires less memory.

Regardless of which approach you choose, it’s important to understand the logic behind Roman numerals and how they work to be able to solve this problem effectively.

Using arrays and switch statements to implement the solution

In order to implement the solution for converting Roman numerals to integers using JavaScript, we can make use of arrays and switch statements for mapping the values of the Roman numerals to their corresponding integer values.

First, we can create two arrays – one to store the Roman numerals and another to store their corresponding integer values. We can use these arrays to map the Roman numerals to integers.

Next, we can iterate through the given Roman numeral string and use a switch statement to check the current Roman numeral character. Depending on the character, we can retrieve the corresponding integer value from the integer array and add it to the result.

Here’s some code to demonstrate this approach:

function romanToInt(s) {
const romanNumerals = [“I”, “V”, “X”, “L”, “C”, “D”, “M”];
const integerValues = [1, 5, 10, 50, 100, 500, 1000];

let result = 0;
let previousValue = 0;

for (let i = s.length – 1; i >= 0; i–) {
const currentRoman = s[i];
const currentIndex = romanNumerals.indexOf(currentRoman);
const currentValue = integerValues[currentIndex];

if (currentValue < previousValue) {
result -= currentValue;
} else {
result += currentValue;

previousValue = currentValue;

return result;

With this implementation, we can easily convert any given Roman numeral string to its corresponding integer value in JavaScript.

An optimized approach using a hash map to solve the problem

When working with large datasets, it is important to optimize your code to ensure that it runs efficiently. One such optimization technique involves using a hash map to solve the problem. In the context of the Roman to Integer LeetCode problem in JavaScript, this technique can significantly speed up your code.

The Roman to Integer problem involves converting a Roman numeral into an integer value. One approach for solving this problem is to create a switch statement that maps each Roman numeral to its corresponding integer value. However, this approach can result in a lot of repetitive code and may not be the most efficient solution.

Instead, using a hash map can simplify the code and make it more efficient. A hash map is a data structure that allows for constant-time lookup of values based on an associated key. In the case of the Roman to Integer problem, we can create a hash map that maps each Roman numeral to its corresponding integer value.

To implement this approach in JavaScript, we can declare a hash map object and populate it with key-value pairs representing each Roman numeral and its corresponding integer value. Then, we can iterate through the input Roman numeral string, checking for the presence of each Roman numeral in the hash map and adding its corresponding integer value to the total.

By using a hash map, we can significantly reduce the amount of repetitive code and improve the efficiency of our solution.

Examples and Test Cases for Roman to Integer Problem in LeetCode with JavaScript

If you are preparing for coding interviews or just want to improve your programming skills, LeetCode is a great platform to practice questions on various topics. One such popular problem on LeetCode is the Roman to Integer problem. Given a Roman numeral, convert it to an integer.

Here are some examples and test cases for the Roman to Integer problem in LeetCode with JavaScript:

  • Input: “III” | Output: 3
  • Input: “IV” | Output: 4
  • Input: “IX” | Output: 9
  • Input: “LVIII” | Output: 58
  • Input: “MCMXCIV” | Output: 1994

Now, let’s take a look at the JavaScript code to solve this problem:

// create a map of Roman numeral symbols and their corresponding values
const romanToIntMap = {
  'I': 1,
  'V': 5,
  'X': 10,
  'L': 50,
  'C': 100,
  'D': 500,
  'M': 1000

const romanToInt = function(s) {
  let sum = 0;
  let prev = 0;
  for (let i = s.length - 1; i >= 0; i--) {
    let curr = romanToIntMap[s[i]];
    if (curr < prev) {
      sum -= curr;
    } else {
      sum += curr;
    prev = curr;
  return sum;

console.log(romanToInt("III")); // output: 3
console.log(romanToInt("IV")); // output: 4
console.log(romanToInt("IX")); // output: 9
console.log(romanToInt("LVIII")); // output: 58
console.log(romanToInt("MCMXCIV")); // output: 1994

By using the map of Roman numeral symbols and their corresponding values, we can easily convert a given Roman numeral into an integer. The code uses a loop to iterate over the characters of the input string and adds or subtracts the corresponding integer values, depending on whether the current value is less than or greater than the previous value.

Using these examples and test cases, you can practice solving the Roman to Integer problem on LeetCode with JavaScript.

Assuming that “Conclusion and key takeaways for practicing LeetCode problems in JavaScript” is a subheading in a blog post titled “Roman to Integer LeetCode JavaScript”, here is the HTML code for the conclusion section:

Conclusion and key takeaways for practicing LeetCode problems in JavaScript

Practicing LeetCode problems in JavaScript can be a great way to improve your problem-solving skills and enhance your understanding of the language. Here are some key takeaways:

  • Start with easy problems and gradually move to harder ones to build your confidence.
  • Use the JavaScript features such as arrays, objects, and ES6 syntax to simplify your code.
  • Practice writing test cases and edge cases to ensure your solutions work for all scenarios.
  • Google is your best friend – don’t be afraid to search for hints and solutions.
  • Lastly, don’t get discouraged if you get stuck on a problem. Keep practicing, and you will eventually succeed!

By following these key takeaways, you can develop a strong foundation in JavaScript programming while also gaining valuable problem-solving skills. Keep practicing and happy coding!

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