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solved: 13. Roman to Integer
Signed-off-by: rajput-hemant <[email protected]>
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‎TOPICWISE.md

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| # | Solution | Tags | Difficulty | Remark |
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| :------: | :-----------------------------------------------------------: | :-------------------------------------------: | :---------: | :----: |
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| **0013** | [Roman to Integer][13] | String, Math, Hash Table | ![][easy] | |
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| **0058** | [Length of Last Word][58] | String | ![][easy] | |
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| **0072** | [Edit Distance][72] | String, DP | ![][hard] | |
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| **0344** | [Reverse String][344] | Two Pointers, String, Recursion | ![][easy] | |
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| # | Solution | Tags | Difficulty | Remark |
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| :------: | :---------------------------------: | :-------------------------------------------: | :---------: | :----: |
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| **0001** | [Two Sum][1] | Array, Hash Table | ![][easy] | |
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| **0013** | [Roman to Integer][13] | String, Math, Hash Table | ![][easy] | |
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| **0389** | [Find the Difference][389] | Hash Table, String, Bit Manipulation, Sorting | ![][easy] | |
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| **0442** | [Find All Duplicates][442] | Array, Hash Table | ![][medium] | |
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| **0653** | [Two Sum IV - Input is a BST ][653] | Tree, DFS, BST, Binary Tree | ![][easy] | |
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| **0002** | [Add Two Numbers][2] | Linked List, Math, Recursion | ![][medium] | |
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| **0007** | [Reverse Integer][7] | Math | ![][medium] | |
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| **0009** | [Palindrome Number][9] | Math | ![][easy] | |
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| **0013** | [Roman to Integer][13] | String, Math, Hash Table | ![][easy] | |
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| **0070** | [Climbing Stairs][70] | Math, DP, Memorization | ![][easy] | |
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| **0172** | [Factorial Trailiing Zeroes][172] | Math | ![][medium] | |
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| **0231** | [Power of Two][231] | Math, Bit Manipulation, Recursion | ![][easy] | |
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[4]: ./src/0001-0100/004%20-%20Median%20of%20Two%20Sorted%20Arrays/
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[7]: ./src//0001-0100/007%20-%20Reverse%20Integer/
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[9]: ./src/0001-0100/009%20-%20Palindrome%20Number/
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[13]: ./src/0001-0100/013%20-%20Roman%20to%20Integer/
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[24]: ./src/0001-0100/024%20-%20Swap%20Nodes%20in%20Pairs/
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[26]: ./src/0001-0100/026%20-%20Remove%20Duplicates%20from%20Sorted%20Array/
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[27]: ./src/0001-0100/027%20-%20Remove%20Element/

‎src/0001-0100/013 - Roman to Integer/README.md

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# 13. Roman to Integer [![share]](https://leetcode.com/problems/roman-to-integer/)
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![][easy]
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## Problem Statement:
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Roman numerals are represented by seven different symbols: `I`, `V`, `X`, `L`, `C`, `D` and `M`.
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```
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Symbol Value
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I 1
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V 5
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X 10
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L 50
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C 100
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D 500
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M 1000
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```
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For example, `2` is written as `II` in Roman numeral, just two ones added together. `12` is written as `XII`, which is simply `X + II`. The number `27` is written as `XXVII`, which is `XX + V + II`.
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Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not `IIII`. Instead, the number four is written as `IV`. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as `IX`. There are six instances where subtraction is used:
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- I can be placed before `V` (5) and `X` (10) to make 4 and 9.
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- X can be placed before `L` (50) and `C` (100) to make 40 and 90.
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- C can be placed before `D` (500) and `M` (1000) to make 400 and 900.
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Given a roman numeral, convert it to an integer.
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### Example 1:
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```
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Input: s = "III"
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Output: 3
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Explanation: III = 3.
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```
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### Example 2:
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```
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Input: s = "LVIII"
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Output: 58
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Explanation: L = 50, V= 5, III = 3.
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```
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### Example 3:
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```
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Input: s = "MCMXCIV"
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Output: 1994
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Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
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```
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### Constraints:
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```- 1 <= s.length <= 15
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- s contains only the characters `('I', 'V', 'X', 'L', 'C', 'D', 'M')`.
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- It is guaranteed that s is a valid roman numeral in the range [`1, 3999]`.
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```
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## Solutions:
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### [_Java_](./RomanToInteger.java)
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```java
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public int romanToInt(String s) {
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Map<Character, Integer> map = Map.of(
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'I', 1,
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'V', 5,
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'X', 10,
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'L', 50,
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'C', 100,
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'D', 500,
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'M', 1000);
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int res = map.get(s.charAt(s.length() - 1));
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for (int i = s.length() - 2; i >= 0; i--) {
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if (map.get(s.charAt(i)) < map.get(s.charAt(i + 1)))
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res -= map.get(s.charAt(i));
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else
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res += map.get(s.charAt(i));
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}
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return res;
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}
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```
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### [_..._]()
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```
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```
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<!----------------------------------{ link }--------------------------------->
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[share]: https://img.icons8.com/external-anggara-blue-anggara-putra/20/000000/external-share-user-interface-basic-anggara-blue-anggara-putra-2.png
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[easy]: https://img.shields.io/badge/Difficulty-Easy-bright.svg
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[medium]: https://img.shields.io/badge/Difficulty-Medium-yellow.svg
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[hard]: https://img.shields.io/badge/Difficulty-Hard-red.svg

‎src/0001-0100/013 - Roman to Integer/RomanToInteger.java

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import java.util.Map;
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public class RomanToInteger {
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public int romanToInt(String s) {
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Map<Character, Integer> map = Map.of(
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'I', 1,
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'V', 5,
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'X', 10,
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'L', 50,
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'C', 100,
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'D', 500,
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'M', 1000);
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int res = map.get(s.charAt(s.length() - 1));
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for (int i = s.length() - 2; i >= 0; i--) {
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if (map.get(s.charAt(i)) < map.get(s.charAt(i + 1)))
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res -= map.get(s.charAt(i));
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else
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res += map.get(s.charAt(i));
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}
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return res;
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}
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}

‎src/README.md

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| **0004** | [Median of Two Sorted Arrays][4] | Array, Binary Search, Divide & Conquer | ![][hard] | |
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| **0007** | [Reverse Integer][7] | Math | ![][medium] | |
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| **0009** | [Palindrome Number][9] | Math | ![][easy] | |
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| **0013** | [Roman to Integer][13] | String, Math, Hash Table | ![][easy] | |
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| **0024** | [Swap Nodes in Pairs][24] | Linked List, Recursion | ![][medium] | |
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| **0026** | [Remove Duplicates][26] | Array, Two Pointers | ![][easy] | |
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| **0027** | [Remove Element][27] | Array, Two Pointers | ![][easy] | |
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[4]: ./0001-0100/004%20-%20Median%20of%20Two%20Sorted%20Arrays/
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[7]: ./0001-0100/007%20-%20Reverse%20Integer/
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[9]: ./0001-0100/009%20-%20Palindrome%20Number/
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[13]: ./0001-0100/013%20-%20Roman%20to%20Integer/
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[24]: ./0001-0100/024%20-%20Swap%20Nodes%20in%20Pairs/
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[26]: ./0001-0100/026%20-%20Remove%20Duplicates%20from%20Sorted%20Array/
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[27]: ./0001-0100/027%20-%20Remove%20Element/

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