Create RegularExpressionMatchingTest.java

Author: kokatesaurabh

src/test/java/com/thealgorithms/dynamicprogramming/RegularExpressionMatchingTest.java

@@ -0,0 +1,151 @@
+package com.thealgorithms.dynamicprogramming;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for RegularExpressionMatching algorithm
+ * 
+ * Covers various test cases including:
+ * - Basic matching scenarios
+ * - '.' wildcard functionality  
+ * - '*' quantifier functionality
+ * - Edge cases and boundary conditions
+ * - Invalid input validation
+ * 
+ * @author Your Name (replace with your GitHub username)
+ */
+public class RegularExpressionMatchingTest {
+
+    @Test
+    void testBasicMatching() {
+        // Exact matches
+        assertTrue(RegularExpressionMatching.isMatch("abc", "abc"));
+        assertFalse(RegularExpressionMatching.isMatch("abc", "abcd"));
+        assertFalse(RegularExpressionMatching.isMatch("abcd", "abc"));
+    }
+
+    @Test
+    void testDotWildcard() {
+        // '.' should match any single character
+        assertTrue(RegularExpressionMatching.isMatch("abc", "a.c"));
+        assertTrue(RegularExpressionMatching.isMatch("axc", "a.c"));
+        assertFalse(RegularExpressionMatching.isMatch("abc", "a.."));
+        assertTrue(RegularExpressionMatching.isMatch("abc", "..."));
+        assertFalse(RegularExpressionMatching.isMatch("ab", "..."));
+    }
+
+    @Test
+    void testStarQuantifier() {
+        // '*' means zero or more of preceding element
+        assertTrue(RegularExpressionMatching.isMatch("aa", "a*"));
+        assertTrue(RegularExpressionMatching.isMatch("aaa", "a*"));
+        assertTrue(RegularExpressionMatching.isMatch("", "a*"));
+        assertFalse(RegularExpressionMatching.isMatch("b", "a*"));
+        
+        // Complex star patterns
+        assertTrue(RegularExpressionMatching.isMatch("aab", "c*a*b"));
+        assertTrue(RegularExpressionMatching.isMatch("b", "c*a*b"));
+    }
+
+    @Test
+    void testDotStarCombination() {
+        // ".*" should match any sequence of characters
+        assertTrue(RegularExpressionMatching.isMatch("abc", ".*"));
+        assertTrue(RegularExpressionMatching.isMatch("xyz", ".*"));
+        assertTrue(RegularExpressionMatching.isMatch("", ".*"));
+        assertTrue(RegularExpressionMatching.isMatch("abc123", ".*"));
+        
+        // More complex combinations
+        assertTrue(RegularExpressionMatching.isMatch("abc", "a.*c"));
+        assertTrue(RegularExpressionMatching.isMatch("axxxc", "a.*c"));
+        assertFalse(RegularExpressionMatching.isMatch("abc", "a.*d"));
+    }
+
+    @Test
+    void testComplexPatterns() {
+        // Mixed patterns
+        assertTrue(RegularExpressionMatching.isMatch("mississippi", "mis*is*ip*."));
+        assertTrue(RegularExpressionMatching.isMatch("mississippi", "mis*is*p*."));
+        assertFalse(RegularExpressionMatching.isMatch("mississippi", "mis*is*ip*.."));
+        
+        // Multiple star operators
+        assertTrue(RegularExpressionMatching.isMatch("a", "a*a*a*"));
+        assertTrue(RegularExpressionMatching.isMatch("aaa", "a*a*a*"));
+        assertTrue(RegularExpressionMatching.isMatch("", "a*b*c*"));
+    }
+
+    @Test
+    void testEdgeCases() {
+        // Empty strings
+        assertTrue(RegularExpressionMatching.isMatch("", ""));
+        assertTrue(RegularExpressionMatching.isMatch("", "a*"));
+        assertTrue(RegularExpressionMatching.isMatch("", ".*"));
+        assertFalse(RegularExpressionMatching.isMatch("", "a"));
+        assertFalse(RegularExpressionMatching.isMatch("", "."));
+        
+        // Single character patterns
+        assertTrue(RegularExpressionMatching.isMatch("a", "a"));
+        assertTrue(RegularExpressionMatching.isMatch("a", "."));
+        assertFalse(RegularExpressionMatching.isMatch("a", "b"));
+        assertFalse(RegularExpressionMatching.isMatch("a", "aa"));
+    }
+
+    @Test
+    void testInvalidInputs() {
+        // Null inputs
+        assertThrows(IllegalArgumentException.class, 
+            () -> RegularExpressionMatching.isMatch(null, "pattern"));
+        assertThrows(IllegalArgumentException.class, 
+            () -> RegularExpressionMatching.isMatch("string", null));
+        assertThrows(IllegalArgumentException.class, 
+            () -> RegularExpressionMatching.isMatch(null, null));
+        
+        // Invalid patterns
+        assertThrows(IllegalArgumentException.class, 
+            () -> RegularExpressionMatching.isMatch("test", "*abc"));
+        assertThrows(IllegalArgumentException.class, 
+            () -> RegularExpressionMatching.isMatch("test", "a**b"));
+        assertThrows(IllegalArgumentException.class, 
+            () -> RegularExpressionMatching.isMatch("test", "abc@"));
+    }
+
+    @Test
+    void testIterativeImplementation() {
+        // Test that iterative implementation produces same results as recursive
+        assertTrue(RegularExpressionMatching.isMatchIterative("aa", "a*"));
+        assertTrue(RegularExpressionMatching.isMatchIterative("ab", ".*"));
+        assertFalse(RegularExpressionMatching.isMatchIterative("aa", "a"));
+        assertTrue(RegularExpressionMatching.isMatchIterative("aab", "c*a*b"));
+        
+        // Test with same inputs for both implementations
+        String[] testStrings = {"", "a", "aa", "ab", "aaa", "aab", "mississippi"};
+        String[] testPatterns = {"", "a", "a*", ".*", "a.b", "c*a*b", "mis*is*p*."};
+        
+        for (String s : testStrings) {
+            for (String p : testPatterns) {
+                if (!p.isEmpty() && p.charAt(0) != '*') { // Skip invalid patterns
+                    boolean recursiveResult = RegularExpressionMatching.isMatch(s, p);
+                    boolean iterativeResult = RegularExpressionMatching.isMatchIterative(s, p);
+                    assertTrue(recursiveResult == iterativeResult, 
+                        String.format("Mismatch for s='%s', p='%s'", s, p));
+                }
+            }
+        }
+    }
+
+    @Test
+    void testLeetCodeExamples() {
+        // Examples from LeetCode problem description
+        assertFalse(RegularExpressionMatching.isMatch("aa", "a"));
+        assertTrue(RegularExpressionMatching.isMatch("aa", "a*"));
+        assertTrue(RegularExpressionMatching.isMatch("ab", ".*"));
+        
+        // Additional LeetCode test cases
+        assertTrue(RegularExpressionMatching.isMatch("aab", "c*a*b"));
+        assertFalse(RegularExpressionMatching.isMatch("mississippi", "mis*is*p*."));
+    }
+}