Add problem 10 - Regular Expression Matching

Author: anirudhology

problems/dynamic_programming/regular_expression_matching.py

@@ -0,0 +1,24 @@
+class RegularExpressionMatching:
+    @staticmethod
+    def isMatch(s: str, p: str) -> bool:
+        # Lengths of strings
+        m, n = len(s), len(p)
+        # Lookup table to store if s[0...i] matches with p[0...j]
+        lookup = [[False] * (n + 1) for _ in range(m + 1)]
+        # Empty string matches with empty pattern
+        lookup[0][0] = True
+        # For empty string and star pattern
+        for j in range(2, n + 1):
+            if p[j - 1] == '*':
+                lookup[0][j] = lookup[0][j - 2]
+        # Populate the remaining table
+        for i in range(1, m + 1):
+            for j in range(1, n + 1):
+                # If characters are same or we have period in pattern
+                if s[i - 1] == p[j - 1] or p[j - 1] == '.':
+                    lookup[i][j] = lookup[i - 1][j - 1]
+                elif j > 1 and p[j - 1] == '*':
+                    lookup[i][j] = lookup[i][j - 2]
+                    if p[j - 2] == '.' or s[i - 1] == p[j - 2]:
+                        lookup[i][j] = lookup[i][j] | lookup[i - 1][j]
+        return lookup[m][n]

tests/dynamic_programming/regular_expression_matching_test.py

@@ -0,0 +1,25 @@
+import unittest
+
+from problems.dynamic_programming.regular_expression_matching import RegularExpressionMatching
+
+
+class TestRegularExpressionMatching(unittest.TestCase):
+
+    def setUp(self):
+        self.regular_expression_matching = RegularExpressionMatching()
+
+    def test_is_match(self):
+        self.assertTrue(self.regular_expression_matching.isMatch("aa", "a*"))
+        self.assertTrue(self.regular_expression_matching.isMatch("ab", ".*"))
+        self.assertFalse(self.regular_expression_matching.isMatch("mississippi", "mis*is*p*."))
+        self.assertTrue(self.regular_expression_matching.isMatch("aab", "c*a*b"))
+        self.assertFalse(self.regular_expression_matching.isMatch("ab", "a"))
+        self.assertTrue(self.regular_expression_matching.isMatch("", ".*"))
+        self.assertTrue(self.regular_expression_matching.isMatch("", "a*"))
+        self.assertFalse(self.regular_expression_matching.isMatch("abcd", "d*"))
+        self.assertTrue(self.regular_expression_matching.isMatch("aaa", "a*a"))
+        self.assertFalse(self.regular_expression_matching.isMatch("aaa", "ab*a"))
+
+
+if __name__ == "__main__":
+    unittest.main()