diff --git a/src/main/java/com/thealgorithms/sorts/SelectionSort.java b/src/main/java/com/thealgorithms/sorts/SelectionSort.java index cc7b3cc6..8c815c6c 100644 --- a/src/main/java/com/thealgorithms/sorts/SelectionSort.java +++ b/src/main/java/com/thealgorithms/sorts/SelectionSort.java @@ -1,46 +1,31 @@ package com.thealgorithms.sorts; public class SelectionSort implements SortAlgorithm { - /** - * Generic selection sort algorithm in increasing order. + * Sorts an array of comparable elements in increasing order using the selection sort algorithm. * - * @param arr the array to be sorted. - * @param the class of array. - * @return sorted array. + * @param array the array to be sorted + * @param the class of array elements + * @return the sorted array */ @Override - public > T[] sort(T[] arr) { - int n = arr.length; - for (int i = 0; i < n - 1; i++) { - int minIndex = i; - for (int j = i + 1; j < n; j++) { - if (arr[minIndex].compareTo(arr[j]) > 0) { - minIndex = j; - } - } - if (minIndex != i) { - SortUtils.swap(arr, i, minIndex); - } + public > T[] sort(T[] array) { + // One by one move the boundary of the unsorted subarray + for (int i = 0; i < array.length - 1; i++) { + + // Swap the remaining minimum element with the current element + SortUtils.swap(array, i, findIndexOfMin(array, i)); } - return arr; + return array; } - /** - * Driver Code - */ - public static void main(String[] args) { - Integer[] arr = {4, 23, 6, 78, 1, 54, 231, 9, 12}; - SelectionSort selectionSort = new SelectionSort(); - Integer[] sorted = selectionSort.sort(arr); - for (int i = 0; i < sorted.length - 1; ++i) { - assert sorted[i] <= sorted[i + 1]; - } - - String[] strings = {"c", "a", "e", "b", "d"}; - String[] sortedStrings = selectionSort.sort(strings); - for (int i = 0; i < sortedStrings.length - 1; ++i) { - assert strings[i].compareTo(strings[i + 1]) <= 0; + private static > int findIndexOfMin(T[] array, final int start) { + int minIndex = start; + for (int i = start + 1; i < array.length; i++) { + if (array[i].compareTo(array[minIndex]) < 0) { + minIndex = i; + } } + return minIndex; } } diff --git a/src/main/java/com/thealgorithms/sorts/SelectionSortRecursive.java b/src/main/java/com/thealgorithms/sorts/SelectionSortRecursive.java index 1326bb5e..32bd58a1 100644 --- a/src/main/java/com/thealgorithms/sorts/SelectionSortRecursive.java +++ b/src/main/java/com/thealgorithms/sorts/SelectionSortRecursive.java @@ -32,13 +32,7 @@ public class SelectionSortRecursive implements SortAlgorithm { return; } - // Find the minimum element in the remaining unsorted array - final int minIndex = findMinIndex(array, index); - - // Swap the found minimum element with the element at the current index - if (minIndex != index) { - SortUtils.swap(array, index, minIndex); - } + SortUtils.swap(array, index, findMinIndex(array, index)); // Recursively call selection sort for the remaining array recursiveSelectionSort(array, index + 1); @@ -47,20 +41,21 @@ public class SelectionSortRecursive implements SortAlgorithm { /** * Finds the index of the minimum element in the array starting from the given index. * - * @param array the array to search in. - * @param start the starting index. - * @param the type of the elements in the array, which must be Comparable. - * @return the index of the minimum element starting from the given index. + * @param array the array to search + * @param start the starting index for the search + * @param the type of elements in the array + * @return the index of the minimum element */ private static > int findMinIndex(T[] array, int start) { - int currentMinIndex = start; - - for (int currentIndex = start + 1; currentIndex < array.length; currentIndex++) { - if (array[currentIndex].compareTo(array[currentMinIndex]) < 0) { - currentMinIndex = currentIndex; - } + // Base case: if start is the last index, return start + if (start == array.length - 1) { + return start; } - return currentMinIndex; + // Recursive call to find the minimum index in the rest of the array + final int minIndexInRest = findMinIndex(array, start + 1); + + // Return the index of the smaller element between array[start] and the minimum element in the rest of the array + return array[start].compareTo(array[minIndexInRest]) < 0 ? start : minIndexInRest; } } diff --git a/src/test/java/com/thealgorithms/sorts/SelectionSortRecursiveTest.java b/src/test/java/com/thealgorithms/sorts/SelectionSortRecursiveTest.java index 48025f4c..20dcf249 100644 --- a/src/test/java/com/thealgorithms/sorts/SelectionSortRecursiveTest.java +++ b/src/test/java/com/thealgorithms/sorts/SelectionSortRecursiveTest.java @@ -5,4 +5,8 @@ public class SelectionSortRecursiveTest extends SortingAlgorithmTest { SortAlgorithm getSortAlgorithm() { return new SelectionSortRecursive(); } + + protected int getGeneratedArraySize() { + return 5000; + } } diff --git a/src/test/java/com/thealgorithms/sorts/SelectionSortTest.java b/src/test/java/com/thealgorithms/sorts/SelectionSortTest.java index 83fbd1ec..fab4be1a 100644 --- a/src/test/java/com/thealgorithms/sorts/SelectionSortTest.java +++ b/src/test/java/com/thealgorithms/sorts/SelectionSortTest.java @@ -1,35 +1,8 @@ package com.thealgorithms.sorts; -import static org.junit.jupiter.api.Assertions.assertArrayEquals; - -import org.junit.jupiter.api.Test; - -class SelectionSortTest { - - @Test - // valid test case - void integerArrTest() { - Integer[] arr = {4, 23, 6, 78, 1, 54, 231, 9, 12}; - SelectionSort selectionSort = new SelectionSort(); - - assertArrayEquals(new Integer[] {1, 4, 6, 9, 12, 23, 54, 78, 231}, selectionSort.sort(arr)); - } - - @Test - // valid test case - void stringArrTest() { - String[] arr = {"c", "a", "e", "b", "d"}; - SelectionSort selectionSort = new SelectionSort(); - - assertArrayEquals(new String[] {"a", "b", "c", "d", "e"}, selectionSort.sort(arr)); - } - - @Test - // invalid test case - void emptyArrTest() { - Integer[] arr = {}; - SelectionSort selectionSort = new SelectionSort(); - - assertArrayEquals(new Integer[] {}, selectionSort.sort(arr)); +class SelectionSortTest extends SortingAlgorithmTest { + @Override + SortAlgorithm getSortAlgorithm() { + return new SelectionSort(); } } diff --git a/src/test/java/com/thealgorithms/sorts/SortingAlgorithmTest.java b/src/test/java/com/thealgorithms/sorts/SortingAlgorithmTest.java index 113bff2b..e6aedc3f 100644 --- a/src/test/java/com/thealgorithms/sorts/SortingAlgorithmTest.java +++ b/src/test/java/com/thealgorithms/sorts/SortingAlgorithmTest.java @@ -11,6 +11,10 @@ import org.junit.jupiter.api.Test; public abstract class SortingAlgorithmTest { abstract SortAlgorithm getSortAlgorithm(); + protected int getGeneratedArraySize() { + return 10_000; + } + @Test void shouldAcceptWhenEmptyArrayIsPassed() { Integer[] array = new Integer[] {}; @@ -153,7 +157,7 @@ public abstract class SortingAlgorithmTest { @Test void shouldAcceptWhenRandomArrayIsPassed() { - int randomSize = SortUtilsRandomGenerator.generateInt(10_000); + int randomSize = SortUtilsRandomGenerator.generateInt(getGeneratedArraySize()); Double[] array = SortUtilsRandomGenerator.generateArray(randomSize); Double[] sorted = getSortAlgorithm().sort(array); assertTrue(SortUtils.isSorted(sorted)); @@ -161,7 +165,7 @@ public abstract class SortingAlgorithmTest { @Test void shouldAcceptWhenRandomListIsPassed() { - int randomSize = SortUtilsRandomGenerator.generateInt(10_000); + int randomSize = SortUtilsRandomGenerator.generateInt(getGeneratedArraySize()); Double[] array = SortUtilsRandomGenerator.generateArray(randomSize); List list = List.of(array); List sorted = getSortAlgorithm().sort(list);