+ * Worst-case performance O(n) + * Best-case performance O(n) + * Average performance O(n) + * Worst-case space complexity O(1) + * + * This class provides a static method to shuffle an array in place. + * + * @author Rashi Dashore (https://github.com/rashi07dashore) + */ +public final class ShuffleArray { + // Prevent instantiation + private ShuffleArray() { + } + + /** + * This method shuffles an array using the Fisher-Yates algorithm. + * + * @param arr is the input array to be shuffled + */ + public static void shuffle(int[] arr) { + Random random = new Random(); + for (int i = arr.length - 1; i > 0; i--) { + int j = random.nextInt(i + 1); + int temp = arr[i]; + arr[i] = arr[j]; + arr[j] = temp; + } + } +} diff --git a/src/test/java/com/thealgorithms/misc/ShuffleArrayTest.java b/src/test/java/com/thealgorithms/misc/ShuffleArrayTest.java new file mode 100644 index 000000000000..915b83e376b6 --- /dev/null +++ b/src/test/java/com/thealgorithms/misc/ShuffleArrayTest.java @@ -0,0 +1,84 @@ +package com.thealgorithms.misc; + +import static org.junit.jupiter.api.Assertions.assertArrayEquals; +import static org.junit.jupiter.api.Assertions.assertNotEquals; +import static org.junit.jupiter.api.Assertions.assertTrue; + +import org.junit.jupiter.api.Test; + +public class ShuffleArrayTest { + + @Test + void testShuffleBasic() { + int[] arr = {1, 2, 3, 4, 5}; + int[] originalArr = arr.clone(); // Clone original array for comparison + ShuffleArray.shuffle(arr); + + // Check that the shuffled array is not the same as the original + assertNotEquals(originalArr, arr); + } + + @Test + void testShuffleSingleElement() { + int[] arr = {1}; + int[] originalArr = arr.clone(); + ShuffleArray.shuffle(arr); + + // Check that the shuffled array is the same as the original + assertArrayEquals(originalArr, arr); + } + + @Test + void testShuffleTwoElements() { + int[] arr = {1, 2}; + int[] originalArr = arr.clone(); + ShuffleArray.shuffle(arr); + + // Check that the shuffled array is not the same as the original + assertNotEquals(originalArr, arr); + // Check that the shuffled array still contains the same elements + assertTrue(arr[0] == 1 || arr[0] == 2); + assertTrue(arr[1] == 1 || arr[1] == 2); + } + + @Test + void testShuffleEmptyArray() { + int[] arr = {}; + int[] originalArr = arr.clone(); + ShuffleArray.shuffle(arr); + + // Check that the shuffled array is the same as the original (still empty) + assertArrayEquals(originalArr, arr); + } + + @Test + void testShuffleLargeArray() { + int[] arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; + int[] originalArr = arr.clone(); + ShuffleArray.shuffle(arr); + + // Check that the shuffled array is not the same as the original + assertNotEquals(originalArr, arr); + } + + @Test + void testShuffleRetainsElements() { + int[] arr = {1, 2, 3, 4, 5}; + ShuffleArray.shuffle(arr); + + // Check that the shuffled array contains the same elements + assertTrue(arr.length == 5); + for (int i = 1; i <= 5; i++) { + assertTrue(contains(arr, i)); + } + } + + private boolean contains(int[] arr, int value) { + for (int num : arr) { + if (num == value) { + return true; + } + } + return false; + } +}
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