Roman to Integer Leetcode Solution: A Step-by-Step Guide

Roman To Integer LeetCode Solution : As developers, we are always looking for ways to improve our coding skills and problem-solving abilities. One way to do this is by practicing on coding platforms like Leetcode, which offers a variety of coding challenges that test our skills in different areas. One such challenge is the Roman to Integer problem, which requires us to convert a given Roman numeral into its corresponding integer value.

Converting Roman numerals to integers may seem like a trivial task, but it can be quite challenging if you are not familiar with the rules and conventions of Roman numerals. The Leetcode Roman to Integer problem is a great way to test your knowledge of Roman numerals and your ability to write efficient and effective code to solve a complex problem.

In this article, we will explore the Leetcode Roman to Integer problem in detail and provide a step-by-step guide to solving it. We will cover the rules and conventions of Roman numerals, explain the problem statement and constraints, and walk through a few different solutions to the problem. By the end of this article, you should have a solid understanding of how to approach the Roman to Integer problem and be ready to tackle similar challenges on Leetcode and other coding platforms.

Problem Statement

What is Roman to Integer Leetcode Solution?

Roman to Integer Leetcode Solution is a problem on the Leetcode platform that requires us to convert Roman numerals to their corresponding integer values. Roman numerals are represented by seven different symbols: I, V, X, L, C, D, and M. Each symbol has a specific value, and the value of a Roman numeral is the sum of the values of its symbols. For example, the Roman numeral IX represents the integer 9 (1 + 8), and the Roman numeral LVIII represents the integer 58 (50 + 5 + 3).

Why is Roman to Integer Leetcode Solution important?

Roman numerals are still used today in various contexts, such as in the numbering of movie sequels, the naming of monarchs, and the dating of historical events. Being able to convert Roman numerals to their corresponding integer values is an important skill for anyone who works with these contexts. Additionally, the Roman to Integer Leetcode Solution problem is a common technical interview question for software engineering positions, so being able to solve it is a valuable skill for job seekers in this field.

Approach

Algorithm

To convert a Roman numeral to an integer, we need to follow the given steps

1. Initialize a map to store the values of each Roman numeral symbol.
2. Traverse the given Roman numeral string from right to left.
3. If the value of the current symbol is less than the value of the next symbol, subtract the value of the current symbol from the result. Otherwise, add the value of the current symbol to the result.
4. Return the final result.

Pseudocode

function romanToInt(s):
    map = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
    result = 0
    prev = 0
    for i in range(len(s)-1, -1, -1):
        curr = map[s[i]]
        if curr < prev:
            result -= curr
        else:
            result += curr
        prev = curr
    return result

The above algorithm takes a Roman numeral string as input and converts it into an integer. We use a dictionary (or map) to store the integer values of each Roman numeral symbol. The result variable is used to accumulate the integer value of the Roman numeral string, while the prev variable is used to keep track of the value of the previous symbol.

We traverse the input string from right to left using a for loop. For each symbol, we look up its integer value in the map. If the value of the current symbol is less than the value of the previous symbol, we subtract it from the result. Otherwise, we add it to the result. Finally, we update the prev variable to the current value and return the result.

Implementation

Code in Python

Our implementation of the Roman to Integer solution in Python is concise and easy to understand. We use a dictionary to map each Roman numeral to its corresponding integer value. Then, we iterate through the input string and sum up the integer values of each Roman numeral. Here is the code:

def romanToInt(s: str) -> int:
    roman_to_int = {'I': 1, 'V': 5, 'X': 10, 'L': 50, 'C': 100, 'D': 500, 'M': 1000}
    result = 0
    prev_value = 0
    for i in range(len(s) - 1, -1, -1):
        curr_value = roman_to_int[s[i]]
        if curr_value < prev_value:
            result -= curr_value
        else:
            result += curr_value
        prev_value = curr_value
    return result

Code in C++

Our implementation of the Roman to Integer solution in C++ is similar to the Python implementation. We use a switch statement to map each Roman numeral to its corresponding integer value. Then, we iterate through the input string and sum up the integer values of each Roman numeral. Here is the code:

int romanToInt(string s) {
    unordered_map roman_to_int = {{'I', 1}, {'V', 5}, {'X', 10}, {'L', 50}, {'C', 100}, {'D', 500}, {'M', 1000}};
    int result = 0;
    int prev_value = 0;
    for (int i = s.length() - 1; i >= 0; i--) {
        int curr_value = roman_to_int[s[i]];
        if (curr_value < prev_value) {
            result -= curr_value;
        } else {
            result += curr_value;
        }
        prev_value = curr_value;
    }
    return result;
}

Code in Java

Our implementation of the Roman to Integer solution in Java is also similar to the Python implementation. We use a HashMap to map each Roman numeral to its corresponding integer value. Then, we iterate through the input string and sum up the integer values of each Roman numeral. Here is the code:

public int romanToInt(String s) {
    Map roman_to_int = new HashMap<>();
    roman_to_int.put('I', 1);
    roman_to_int.put('V', 5);
    roman_to_int.put('X', 10);
    roman_to_int.put('L', 50);
    roman_to_int.put('C', 100);
    roman_to_int.put('D', 500);
    roman_to_int.put('M', 1000);
    int result = 0;
    int prev_value = 0;
    for (int i = s.length() - 1; i >= 0; i--) {
        int curr_value = roman_to_int.get(s.charAt(i));
        if (curr_value < prev_value) {
            result -= curr_value;
        } else {
            result += curr_value;
        }
        prev_value = curr_value;
    }
    return result;
}

Complexity Analysis

When solving Leetcode problems, it is important to analyze the time and space complexity of our solution. Here, we will discuss the complexity analysis of the Roman to Integer Leetcode solution.

Time Complexity

The time complexity of our solution is determined by the number of operations performed as a function of the input size. In the case of the Roman to Integer problem, we traverse the string once to convert the Roman numerals to integers. Since we have an integer limit of less than 4000, the string size will always be a constant value. Therefore, the time complexity is O(1).

Space Complexity

The space complexity of our solution is determined by the amount of memory used as a function of the input size. In the case of the Roman to Integer problem, we only use constant memory space. We store the Roman symbols and their corresponding integer values in a map or dictionary, but there are only 7 symbols, hence the worst-case space complexity can be O(7) which is equivalent to O(1).

Therefore, the overall space complexity of our solution is O(1).

Overall, the Roman to Integer problem has a time complexity of O(1) and a space complexity of O(1). This means that our solution is efficient and can handle large inputs without running out of memory or taking too much time to execute. 

Conclusion

In conclusion, the Roman to Integer problem on Leetcode is a challenging problem that requires a deep understanding of Roman numerals and their corresponding integer values. We have explored various solutions to this problem, including left-to-right pass and mapping techniques, which can help us convert Roman numerals to integers. Through our research and analysis of the various solutions available, we have found that the left-to-right pass technique is the most efficient and effective way to solve this problem. This technique allows us to keep track of the current and previous values and subtract the previous value from the current value if it is smaller. In addition, we have learned that the problem constraints are important to consider when developing a solution. The input string can be up to 15 characters long, and the output integer must be between 1 and 3999. Therefore, we must ensure that our solution can handle all possible input strings and produce the correct output integer within the given constraints. Overall, the Roman to Integer problem on Leetcode is an excellent way to practice our problem-solving skills and deepen our understanding of Roman numerals and their corresponding integer values. With the right techniques and problem-solving approach, we can solve this problem efficiently and effectively.