Added RemoveStars.java and ComplexNumberMultiplication.java

Author: SwarritSrivastava

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

@@ -0,0 +1,33 @@
+package com.thealgorithms.strings;
+/**
+ * @author Swarit Srivastava (https://github.com/SwarritSrivastava)
+ */
+public final class ComplexNumberMultiplication {
+    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.
+     */
+    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);
+        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

@@ -0,0 +1,35 @@
+package com.thealgorithms.strings;
+/**
+ * @author Swarit Srivastava (https://github.com/SwarritSrivastava)
+ */
+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.
+     */
+    public static String removeStars(String input) {
+        if (input == null || input.isEmpty()) {
+            return input;
+        }
+        int n = input.length();
+        StringBuilder ans = new StringBuilder();
+        for (int i = 0; i < n; i++) {
+            char t = input.charAt(i);
+            if (t != '*') {
+                ans.append(t);
+            }
+            else {
+                ans.deleteCharAt(ans.length() - 1);
+            }
+        }
+        return ans.toString();
+    }
+}