2022-10-09 update: added "Regular Expression Matching" (#129)

Author: fartem

Diff for: README.md

@@ -717,6 +717,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | Name                                          | Link to LeetCode                                                                 | Link to solution                                                                                          |
 |-----------------------------------------------|----------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------|
 | 4. Median of Two Sorted Arrays                | [Link](https://leetcode.com/problems/median-of-two-sorted-arrays/)               | [Link](./src/main/java/com/smlnskgmail/jaman/leetcodejava/hard/MedianOfTwoSortedArrays.java)              |
+| 10. Regular Expression Matching               | [Link](https://leetcode.com/problems/regular-expression-matching/)               | [Link](./src/main/java/com/smlnskgmail/jaman/leetcodejava/hard/RegularExpressionMatching.java)            |
 | 23. Merge k Sorted Lists                      | [Link](https://leetcode.com/problems/merge-k-sorted-lists/)                      | [Link](./src/main/java/com/smlnskgmail/jaman/leetcodejava/hard/MergeKSortedLists.java)                    |
 | 25. Reverse Nodes in k-Group                  | [Link](https://leetcode.com/problems/reverse-nodes-in-k-group/)                  | [Link](./src/main/java/com/smlnskgmail/jaman/leetcodejava/hard/ReverseNodesInKGroup.java)                 |
 | 30. Substring with Concatenation of All Words | [Link](https://leetcode.com/problems/substring-with-concatenation-of-all-words/) | [Link](./src/main/java/com/smlnskgmail/jaman/leetcodejava/hard/SubstringWithConcatenationOfAllWords.java) |

Diff for: src/main/java/com/smlnskgmail/jaman/leetcodejava/hard/RegularExpressionMatching.java

@@ -0,0 +1,29 @@
+package com.smlnskgmail.jaman.leetcodejava.hard;
+
+// https://leetcode.com/problems/regular-expression-matching/
+public class RegularExpressionMatching {
+
+    private final String s;
+    private final String p;
+
+    public RegularExpressionMatching(String s, String p) {
+        this.s = s;
+        this.p = p;
+    }
+
+    public boolean solution() {
+        return isMatch(s, p);
+    }
+
+    private boolean isMatch(String s, String p) {
+        if (p.isEmpty()) {
+            return s.isEmpty();
+        }
+        boolean m = !s.isEmpty() && (p.charAt(0) == s.charAt(0) || p.charAt(0) == '.');
+        if (p.length() >= 2 && p.charAt(1) == '*') {
+            return isMatch(s, p.substring(2)) || (m && isMatch(s.substring(1), p));
+        }
+        return m && isMatch(s.substring(1), p.substring(1));
+    }
+
+}

Diff for: src/test/java/com/smlnskgmail/jaman/leetcodejava/hard/RegularExpressionMatchingTest.java

@@ -0,0 +1,14 @@
+package com.smlnskgmail.jaman.leetcodejava.hard;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+
+public class RegularExpressionMatchingTest {
+
+    @Test
+    public void defaultTest() {
+        assertFalse(new RegularExpressionMatching("aa", "a").solution());
+    }
+
+}