DEV: Implementing Alternative String Arrange

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

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+package com.thealgorithms.strings;
+
+/**
+ * This class provides a method to arrange two strings by alternating their characters.
+ * If one string is longer, the remaining characters of the longer string are appended at the end.
+ * <p>
+ * Example:
+ * Input: "abc", "12345"
+ * Output: "a1b2c345"
+ * <p>
+ * Input: "abcd", "12"
+ * Output: "a1b2cd"
+ *
+ * @author Milad Sadeghi
+ */
+public final class AlternativeStringArrange {
+
+    // Private constructor to prevent instantiation
+    private AlternativeStringArrange() {
+    }
+
+    /**
+     * Arranges two strings by alternating their characters.
+     *
+     * @param firstString  the first input string
+     * @param secondString the second input string
+     * @return a new string with characters from both strings arranged alternately
+     */
+    public static String arrange(String firstString, String secondString) {
+        StringBuilder result = new StringBuilder();
+        int length1 = firstString.length();
+        int length2 = secondString.length();
+        int minLength = Math.min(length1, length2);
+
+        for (int i = 0; i < minLength; i++) {
+            result.append(firstString.charAt(i));
+            result.append(secondString.charAt(i));
+        }
+
+        if (length1 > length2) {
+            result.append(firstString.substring(minLength));
+        } else if (length2 > length1) {
+            result.append(secondString.substring(minLength));
+        }
+
+        return result.toString();
+    }
+}

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

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+package com.thealgorithms.strings;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.stream.Stream;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+class AlternativeStringArrangeTest {
+
+    // Method to provide test data
+    private static Stream<Object[]> provideTestData() {
+        return Stream.of(new Object[] {"abc", "12345", "a1b2c345"}, new Object[] {"abcd", "12", "a1b2cd"}, new Object[] {"", "123", "123"}, new Object[] {"abc", "", "abc"}, new Object[] {"a", "1", "a1"}, new Object[] {"ab", "12", "a1b2"}, new Object[] {"abcdef", "123", "a1b2c3def"},
+            new Object[] {"ab", "123456", "a1b23456"});
+    }
+
+    // Parameterized test using the provided test data
+    @ParameterizedTest(name = "{0} and {1} should return {2}")
+    @MethodSource("provideTestData")
+    void arrangeTest(String input1, String input2, String expected) {
+        assertEquals(expected, AlternativeStringArrange.arrange(input1, input2));
+    }
+}