Added RemoveStarsTest.java and ComplexNumberMultiplicationTest.java

Author: SwarritSrivastava

src/main/java/com/thealgorithms/strings/ComplexNumberMultiplication.java

@@ -7,27 +7,40 @@ private ComplexNumberMultiplication() {
 
     }
     /**
-     * Multiplies two Complex numbers given as Strings Where,
-     * real part of each number ranges from [-100,100]
-     * imaginary part of each number ranges from [-100,100]
-     * i*i = -1;
-     * @param num1 The first complex number.
-     * @param num2 The second complex number.
-     * @return A string containing the multiplied complex number.
+     * Multiplies two complex numbers given as strings.
+     * <p>
+     * Each complex number is represented in the form "real+imaginaryi" where:
+     * <ul>
+     *   <li>real is the real part and is an integer in the range [-100, 100]</li>
+     *   <li>imaginary is the imaginary part and is an integer in the range [-100, 100]</li>
+     *   <li>i * i = -1</li>
+     * </ul>
+     *
+     * Example: {@code multiplyComplexNumbers("1+1i", "1+1i") -> "0+2i"}
+     *
+     * @param num1 the first complex number
+     * @param num2 the second complex number
+     * @return the resulting complex number after multiplication
      */
     public static String multiplyComplexNumbers(String num1, String num2) {
         int i = num1.indexOf('+');
         int j = num2.indexOf('+');
+
         String r1 = num1.substring(0, i);
         String i1 = num1.substring(i + 1, num1.length() - 1);
-        String r2 = num2.substring(0, j);
-        String i2 = num2.substring(j + 1, num2.length() - 1);
+
         int re1 = Integer.parseInt(r1);
         int im1 = Integer.parseInt(i1);
+
+        String r2 = num2.substring(0, j);
+        String i2 = num2.substring(j + 1, num2.length() - 1);
+
         int re2 = Integer.parseInt(r2);
         int im2 = Integer.parseInt(i2);
+
         int reAns = re1 * re2 - im1 * im2;
         int imAns = re1 * im2 + im1 * re2;
+
         return reAns + "+" + imAns + "i";
     }
 }

src/main/java/com/thealgorithms/strings/RemoveStars.java

@@ -6,14 +6,18 @@ public final class RemoveStars {
     private RemoveStars() {
     }
     /**
-     * Removes * characters from the given string. According to the follwing rules
-     * You are given a string s, which contains stars *.
-     * In one operation, you can:
-     * Choose a star in s.
-     * Remove the closest non-star character to its left, as well as remove the star itself.
-     * Return the string after all stars have been removed.
-     * @param input The input string from which duplicate characters need to be removed.
-     * @return A string containing no stars as per the given constraints.
+     * Removes stars ('*') from the given string according to the following rules:
+     * <ul>
+     *   <li>For each star in the string, remove the closest non-star character to its left
+     *       along with the star itself.</li>
+     *   <li>Return the final string after performing all removals.</li>
+     *   <li>Given that such operation is always possible for the input</li>
+     * </ul>
+     *
+     * Example: {@code "leet**cod*e" -> "lecoe"}
+     *
+     * @param input The input string possibly containing '*' characters.
+     * @return The resulting string after removing stars as per the rules.
      */
     public static String removeStars(String input) {
         if (input == null || input.isEmpty()) {

src/test/java/com/thealgorithms/strings/ComplexNumberMultiplicationTest.java

@@ -0,0 +1,27 @@
+package com.thealgorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import org.junit.jupiter.api.Test;
+
+class ComplexNumberMultiplicationTest {
+
+    @Test
+    void testExample() {
+        assertEquals("0+2i", ComplexNumberMultiplication.multiplyComplexNumbers("1+1i", "1+1i"));
+    }
+
+    @Test
+    void testNegative() {
+        assertEquals("2+0i", ComplexNumberMultiplication.multiplyComplexNumbers("1+1i", "1+-1i"));
+    }
+
+    @Test
+    void testZero() {
+        assertEquals("0+0i", ComplexNumberMultiplication.multiplyComplexNumbers("0+0i", "5+5i"));
+    }
+
+    @Test
+    void testDifferentValues() {
+        assertEquals("5+5i", ComplexNumberMultiplication.multiplyComplexNumbers("1+2i", "3+-1i"));
+    }
+}

src/test/java/com/thealgorithms/strings/RemoveStarsTest.java

@@ -0,0 +1,33 @@
+package com.thealgorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import org.junit.jupiter.api.Test;
+
+class RemoveStarsTest {
+
+    @Test
+    void testExample() {
+        assertEquals("lecoe", RemoveStars.removeStars("leet**cod*e"));
+    }
+
+    @Test
+    void testMultipleStars() {
+        assertEquals("c", RemoveStars.removeStars("ab*c*d**c"));
+    }
+
+    @Test
+    void testEmptyInput() {
+        assertEquals("", RemoveStars.removeStars(""));
+    }
+
+    @Test
+    void testNullInput() {
+        assertNull(RemoveStars.removeStars(null));
+    }
+
+    @Test
+    void testNoStars() {
+        assertEquals("hello", RemoveStars.removeStars("hello"));
+    }
+}