From 7a5fe92b2ac96d9a2e6e571285f3a188d7ea01ea Mon Sep 17 00:00:00 2001 From: Alex Klymenko Date: Sat, 10 Aug 2024 09:25:46 +0200 Subject: [PATCH] feat: `FlashSort` implementation (#5305) --- DIRECTORY.md | 2 + .../com/thealgorithms/sorts/FlashSort.java | 206 ++++++++++++++++++ .../thealgorithms/sorts/FlashSortTest.java | 90 ++++++++ 3 files changed, 298 insertions(+) create mode 100644 src/main/java/com/thealgorithms/sorts/FlashSort.java create mode 100644 src/test/java/com/thealgorithms/sorts/FlashSortTest.java diff --git a/DIRECTORY.md b/DIRECTORY.md index 22453235b..656597c3b 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -501,6 +501,7 @@ * [DualPivotQuickSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/DualPivotQuickSort.java) * [DutchNationalFlagSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/DutchNationalFlagSort.java) * [ExchangeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/ExchangeSort.java) + * [FlashSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/FlashSort.java) * [GnomeSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/GnomeSort.java) * [HeapSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/HeapSort.java) * [InsertionSort](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/sorts/InsertionSort.java) @@ -874,6 +875,7 @@ * [DualPivotQuickSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/DualPivotQuickSortTest.java) * [DutchNationalFlagSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/DutchNationalFlagSortTest.java) * [ExchangeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/ExchangeSortTest.java) + * [FlashSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/FlashSortTest.java) * [GnomeSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/GnomeSortTest.java) * [HeapSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/HeapSortTest.java) * [InsertionSortTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/sorts/InsertionSortTest.java) diff --git a/src/main/java/com/thealgorithms/sorts/FlashSort.java b/src/main/java/com/thealgorithms/sorts/FlashSort.java new file mode 100644 index 000000000..e8dbf8c42 --- /dev/null +++ b/src/main/java/com/thealgorithms/sorts/FlashSort.java @@ -0,0 +1,206 @@ +package com.thealgorithms.sorts; + +/** + * Implementation of Flash Sort algorithm that implements the SortAlgorithm interface. + * + * Sorts an array using the Flash Sort algorithm. + *

+ * Flash Sort is a distribution sorting algorithm that partitions the data into + * different classes based on a classification array. It performs the sorting by + * first distributing the data elements into different buckets (or classes) and + * then permuting these buckets into the sorted order. + *

+ * The method works as follows: + *

    + *
  1. Finds the minimum and maximum values in the array.
    2. + *
  2. Initializes a classification array `L` to keep track of the number of elements in each class.
    3. + *
  3. Computes a normalization constant `c1` to map elements into classes.
    4. + *
  4. Classifies each element of the array into the corresponding bucket in the classification array.
    5. + *
  5. Transforms the classification array to compute the starting indices of each bucket.
    6. + *
  6. Permutes the elements of the array into sorted order based on the classification.
    7. + *
  7. Uses insertion sort for the final arrangement to ensure complete sorting.
    8. + *
+ */ +public class FlashSort implements SortAlgorithm { + private double classificationRatio = 0.45; + + public FlashSort() { + } + + public FlashSort(double classificationRatio) { + if (classificationRatio <= 0 || classificationRatio >= 1) { + throw new IllegalArgumentException("Classification ratio must be between 0 and 1 (exclusive)."); + } + this.classificationRatio = classificationRatio; + } + + public double getClassificationRatio() { + return classificationRatio; + } + + public void setClassificationRatio(double classificationRatio) { + if (classificationRatio <= 0 || classificationRatio >= 1) { + throw new IllegalArgumentException("Classification ratio must be between 0 and 1 (exclusive)."); + } + this.classificationRatio = classificationRatio; + } + + /** + * Sorts an array using the Flash Sort algorithm. + * + * @param array the array to be sorted. + * @param the type of elements to be sorted, must be comparable. + * @return the sorted array. + */ + @Override + public > T[] sort(T[] array) { + flashSort(array); + return array; + } + + /** + * Sorts an array using the Flash Sort algorithm. + * + * @param arr the array to be sorted. + * @param the type of elements to be sorted, must be comparable. + */ + private > void flashSort(T[] arr) { + if (arr.length == 0) { + return; + } + + final T min = findMin(arr); + final int maxIndex = findMaxIndex(arr); + + if (arr[maxIndex].compareTo(min) == 0) { + return; // All elements are the same + } + + final int m = (int) (classificationRatio * arr.length); + + final int[] classificationArray = new int[m]; + + final double c1 = (double) (m - 1) / arr[maxIndex].compareTo(min); + + classify(arr, classificationArray, c1, min); + + transform(classificationArray); + + permute(arr, classificationArray, c1, min, arr.length, m); + + insertionSort(arr); + } + + /** + * Finds the minimum value in the array. + * + * @param arr the array to find the minimum value in. + * @param the type of elements in the array, must be comparable. + * @return the minimum value in the array. + */ + private > T findMin(final T[] arr) { + T min = arr[0]; + for (int i = 1; i < arr.length; i++) { + if (arr[i].compareTo(min) < 0) { + min = arr[i]; + } + } + return min; + } + + /** + * Finds the index of the maximum value in the array. + * + * @param arr the array to find the maximum value index in. + * @param the type of elements in the array, must be comparable. + * @return the index of the maximum value in the array. + */ + private > int findMaxIndex(final T[] arr) { + int maxIndex = 0; + for (int i = 1; i < arr.length; i++) { + if (arr[i].compareTo(arr[maxIndex]) > 0) { + maxIndex = i; + } + } + return maxIndex; + } + + /** + * Classifies elements of the array into the classification array classificationArray. + * + * @param arr the array to be classified. + * @param classificationArray the classification array holding the count of elements in each class. + * @param c1 the normalization constant used to map the elements to the classification array. + * @param min the minimum value in the array. + * @param the type of elements in the array, must be comparable. + */ + private > void classify(final T[] arr, final int[] classificationArray, final double c1, final T min) { + for (int i = 0; i < arr.length; i++) { + int k = (int) (c1 * arr[i].compareTo(min)); + classificationArray[k]++; + } + } + + /** + * Transforms the classification array classificationArray into the starting index array. + * + * @param classificationArray the classification array holding the count of elements in each class. + */ + private void transform(final int[] classificationArray) { + for (int i = 1; i < classificationArray.length; i++) { + classificationArray[i] += classificationArray[i - 1]; + } + } + + /** + * Permutes the array into sorted order based on the classification array classificationArray. + * + * @param arr the array to be permuted. + * @param classificationArray the classification array holding the count of elements in each class. + * @param c1 the normalization constant used to map the elements to the classification array. + * @param min the minimum value in the array. + * @param n the length of the array. + * @param m the number of classes in the classification array. + * @param the type of elements in the array, must be comparable. + */ + private > void permute(final T[] arr, final int[] classificationArray, final double c1, T min, int n, int m) { + int move = 0; + int j = 0; + int k = m - 1; + T flash; + while (move < n - 1) { + while (j > classificationArray[k] - 1) { + j++; + k = (int) (c1 * arr[j].compareTo(min)); + } + flash = arr[j]; + while (j != classificationArray[k]) { + k = (int) (c1 * flash.compareTo(min)); + T temp = arr[classificationArray[k] - 1]; + arr[classificationArray[k] - 1] = flash; + flash = temp; + classificationArray[k]--; + move++; + } + } + } + + /** + * Sorts an array using the insertion sort algorithm. + * + * @param arr the array to be sorted. + * @param the type of elements to be sorted, must be comparable. + */ + private > void insertionSort(final T[] arr) { + int n = arr.length; + for (int i = 1; i < n; i++) { + T key = arr[i]; + int j = i - 1; + while (j >= 0 && arr[j].compareTo(key) > 0) { + arr[j + 1] = arr[j]; + j--; + } + arr[j + 1] = key; + } + } +} diff --git a/src/test/java/com/thealgorithms/sorts/FlashSortTest.java b/src/test/java/com/thealgorithms/sorts/FlashSortTest.java new file mode 100644 index 000000000..6b1a74403 --- /dev/null +++ b/src/test/java/com/thealgorithms/sorts/FlashSortTest.java @@ -0,0 +1,90 @@ +package com.thealgorithms.sorts; + +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertThrows; + +import java.lang.reflect.Method; +import java.util.ArrayList; +import java.util.Collection; +import java.util.List; +import org.junit.jupiter.api.DynamicTest; +import org.junit.jupiter.api.Test; +import org.junit.jupiter.api.TestFactory; +import org.junit.jupiter.api.function.Executable; +import org.junit.jupiter.params.ParameterizedTest; +import org.junit.jupiter.params.provider.ValueSource; + +public class FlashSortTest extends SortingAlgorithmTest { + private final FlashSort flashSort = new FlashSort(); + + public FlashSort getFlashSort() { + return flashSort; + } + + @Override + SortAlgorithm getSortAlgorithm() { + return getFlashSort(); + } + + @Test + public void testDefaultConstructor() { + double defaultRation = 0.45; + FlashSort sorter = new FlashSort(); + assertEquals(defaultRation, sorter.getClassificationRatio()); + } + + @ParameterizedTest + @ValueSource(doubles = {0.1, 0.2, 0.5, 0.9}) + public void testCustomConstructorValidRatio(double ratio) { + FlashSort sorter = new FlashSort(ratio); + assertEquals(ratio, sorter.getClassificationRatio()); + } + + @ParameterizedTest + @ValueSource(doubles = {0, 1, -0.1, 1.1}) + public void testCustomConstructorInvalidRatio(double ratio) { + assertThrows(IllegalArgumentException.class, () -> new FlashSort(ratio)); + } + + @TestFactory + public Collection dynamicTestsForSorting() { + List dynamicTests = new ArrayList<>(); + double[] ratios = {0.1, 0.2, 0.5, 0.9}; + + for (double ratio : ratios) { + FlashSort sorter = (FlashSort) getSortAlgorithm(); + sorter.setClassificationRatio(ratio); + dynamicTests.addAll(createDynamicTestsForRatio(ratio)); + } + + return dynamicTests; + } + + private Collection createDynamicTestsForRatio(double ratio) { + List dynamicTests = new ArrayList<>(); + for (TestMethod testMethod : getTestMethodsFromSuperClass()) { + dynamicTests.add(DynamicTest.dynamicTest("Ratio: " + ratio + " - Test: " + testMethod.name(), testMethod.executable())); + } + return dynamicTests; + } + + private List getTestMethodsFromSuperClass() { + List testMethods = new ArrayList<>(); + Method[] methods = SortingAlgorithmTest.class.getDeclaredMethods(); + for (Method method : methods) { + if (method.isAnnotationPresent(Test.class)) { + testMethods.add(new TestMethod(() -> { + try { + method.invoke(this); + } catch (Exception e) { + throw new RuntimeException(e); + } + }, method.getName())); + } + } + return testMethods; + } + + record TestMethod(Executable executable, String name) { + } +}