Create a hash map storing each Roman numeral character and its integer value. Initialize the result to 0. ... If the current character's value is less than the next character's value, subtract it from the result. Otherwise, add it to the result. Return the final result.

Therefore, the overall space complexity is O(m), where m represents the size of the character set used in the Roman numeral system. Pattern Learn more about how to find time and space complexity quickly. The pairwise function is only available in Python 3.10+. If you're using an earlier version or submitting to a platform that doesn't support Python 3.10, the code will fail with an ImportError. Solution: Compare each character with its right neighbor using an index loop:

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Solutions · Submissions · Submissions · 13. Roman to Integer · Easy · Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 · For example, 2 is written as II in Roman numeral, just two ones added together.

public class Solution { public int RomanToInt(string s) { Dictionary<char, int> d = new Dictionary<char, int>(); d.Add('I', 1); d.Add('V', 5); d.Add('X', 10); d.Add('L', 50); d.Add('C', 100); d.Add('D', 500); d.Add('M', 1000); int ans = d[s[s.Length - 1]]; for (int i = 0; i < s.Length - 1; ++i) { int sign = d[s[i]] < d[s[i + 1]] ? -1 : 1; ans += sign * d[s[i]]; } return ans; } } class Solution { /** * @param String $s * @return Integer */ function romanToInt($s) { $d = [ 'I' => 1, 'V' => 5, 'X' => 10, 'L' => 50, 'C' => 100, 'D' => 500, 'M' => 1000, ]; $ans = 0; $len = strlen($s); for ($i = 0; $i < $len - 1; $i++) { if ($d[$s[$i]] < $d[$s[$i + 1]]) { $ans -= $d[$s[$i]]; } else { $ans += $d[$s[$i]]; } } $ans += $d[$s[$len - 1]]; return $ans; } }

December 22, 2025 - The C solution takes a more brute force approach by explicitly checking for all subtractive combinations. Step 1: Create a hash map (or equivalent) to store the integer value of each Roman numeral symbol.

October 14, 2022 - class Solution: def romanToInt(self, ... · Note: This problem 13. Roman to Integer is generated by Leetcode but the solution is provided by CodingBroz....

LeetCode problem ↗ Solution code · Understand the problem: Convert a Roman numeral string s to its integer value. Create a dictionary d mapping Roman numerals to their values: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Initialize a variable summ to 0 to store the total value and an index i to 0.

January 31, 2023 - We all know that one could simply go to the next tab and check the solution, so why would I be solving it again here? The answer is 1: to provide a more in-depth and/or slow-paced explanation; and 2: to hopefully learn and memorize it better myself. The problem number 13 invites you to build a function capable of, given a string input representing a roman numeral, return it’s equivalent in integers.

May 21, 2026 - Hey there, future coding superstar! 👋 Ever looked at Roman numerals and thought, "That's a cool system, but how would I code that conversion?" Today, we're diving into LeetCode problem #13, "Roman to Integer," a fantastic problem for beginners that teaches some core programming concepts.

Input is guaranteed to be within the range from 1 to 3999. ... Input: "LVIII" Output: 58 Explanation: L = 50, V= 5, III = 3. ... Input: "MCMXCIV" Output: 1994 Explanation: M = 1000, CM = 900, XC = 90 and IV = 4. Approach 1: Scan each character and check its relationship with the pervious one.

December 22, 2024 - Return the Total: After traversing the string, total holds the integer equivalent. ... Clarify constraints: Confirm that the Roman numeral input will always be valid (as per problem assumptions). Highlight efficiency: Emphasize O(n) time complexity and how the subtractive rule is handled efficiently. ... Smallest numeral ("I" → 1). Mixed additive and subtractive cases ("XIV" → 14). ... Check out the full explanation and code walkthrough on my Dev.to post: 👉 Trapping Rain Water - JavaScript Solution

January 28, 2024 - Problem statement Roman numerals are represented by seven symbols: I, V, X, L, C, D, and M. Symbol Value I 1 V 5 X 10 L 50 C 100 D 500 M 1000 For example, 2 is...

August 4, 2025 - This solution beat 99.94% of submissions for time This solution beat 77.21% of submissions for memory usage at time of writing. Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M. ... There are six instances where subtraction is used: I can be placed before V (5) and X (10) to make 4 and 9. X can be placed before L (50) and C (100) to make 40 and 90. C can be placed before D (500) and M (1000) to make 400 and 900. Given a roman numeral, convert it to an integer.

September 1, 2025 - Mapping: roman_map assigns values to Roman symbols. ... If the current numeral is smaller than the next, subtract it (IV → -1 + 5 = 4). Otherwise, add it normally (VI → 5 + 1 = 6). Result: The accumulated total gives the integer equivalent.

August 21, 2022 - The one thing we should realize about the subtractive numerals is that they're identifiable because they appear before a larger number. This means that the easier way to iterate through roman numerals is from right to left, to aid in the identifying process.

Given a roman numeral, convert it to an integer.

December 15, 2022 - Since generally roman numerals are written largest to smallest usually except some cases where subtraction is needed, I can just check the case that if current char value is greater than next char value, if yes than i can…

December 10, 2025 - Input: s = "III" Output: 3 Explanation: III = 3. Input: s = "LVIII" Output: 58 Explanation: L = 50, V= 5, III = 3. Input: s = "MCMXCIV" Output: 1994 Explanation: M = 1000, CM = 900, XC = 90 and IV = 4. Initially, I could not figure out where ...

November 4, 2020 - For this super simple solution, we loop through the characters of the provided string, and for each one we check whether that character is worth more or less than the next one (if the next one exists).