Added solution for Roman To Integer

Author: PalmaAnd

Java/src/main/java/problems/leetcode/hash_table/RomanToInteger.java

@@ -0,0 +1,26 @@
+package problems.leetcode.hash_table;
+
+public class RomanToInteger {
+    public int romanToInt(String s) {
+        int result = 0, previous = 0, current = 0;
+        char[] chars = s.toCharArray();
+        for (char romanChar : chars) {
+            switch (romanChar) {
+                case 'I' -> current = 1;
+                case 'V' -> current = 5;
+                case 'X' -> current = 10;
+                case 'L' -> current = 50;
+                case 'C' -> current = 100;
+                case 'D' -> current = 500;
+                case 'M' -> current = 1000;
+            }
+            if (previous < current)
+                // because we add previous once before and need to remove that
+                result += current - 2 * previous;
+            else
+                result += current;
+            previous = current;
+        }
+        return result;
+    }
+}

Java/src/test/java/problems/leetcode/hash_table/RomanToIntegerTest.java

@@ -0,0 +1,33 @@
+package problems.leetcode.hash_table;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class RomanToIntegerTest {
+
+    @Test
+    void testSimple() {
+        RomanToInteger romanToInteger = new RomanToInteger();
+        String input = "III";
+        int result = romanToInteger.romanToInt(input);
+        assertEquals(3, result);
+    }
+
+    @Test
+    void testMultipleSymbols() {
+        RomanToInteger romanToInteger = new RomanToInteger();
+        String input = "MDCLXVI";
+        int result = romanToInteger.romanToInt(input);
+        assertEquals(1666, result);
+    }
+
+    @Test
+    void testComplexString() {
+        RomanToInteger romanToInteger = new RomanToInteger();
+        String input = "MCMXCIV";
+        int result = romanToInteger.romanToInt(input);
+        assertEquals(1994, result);
+    }
+}

README.md

@@ -3,6 +3,7 @@
 This repository contains my solutions to various LeetCode problems. The solutions are implemented in both Java and JavaScript. The Java solutions are located in the `Java/src/` directory, while the JavaScript solutions are divided into problem implementations in `js/Problems/` and corresponding Jest test cases in `js/Tests/`.
 
 ## Links to my profiles
+
 - [Project Euler](https://projecteuler.net/progress=PalmaAnd)
 - [LeetCode](https://leetcode.com/PalmaAnd/)
 
@@ -41,6 +42,7 @@ Here is a list of the problems I've solved along with links to the corresponding
 | [Evaluate Reverse Polish Notation](https://leetcode.com/problems/evaluate-reverse-polish-notation/)   | [Java](Java/src/main/java/problems/leetcode/stack/ReversePolish.java)              |
 | [3Sum](https://leetcode.com/problems/3sum/)                                                           | [Java](Java/src/main/java/problems/leetcode/two_pointers/ThreeSum.java)            |
 | [Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix)                          | [Java](Java/src/main/java/problems/leetcode/others/LongestCommonPrefix.java)       |
+| [Roman to Integer](https://leetcode.com/problems/roman-to-integer)                                    | [Java](Java/src/main/java/problems/leetcode/hash_table/RomanToInteger.java)        |
 
 ## Java Solutions