Modify Insertion sort implementation to classical one + add function insertion-sentinel sort. (#3622)

* bug fix for CircularBuffer + refactoring + add unit tests

* change Insertion sort to classical implementation + add isSorted function to SortUtils + add SortUtilsRandomGenerator for generating random values and arrays

* little fix

Co-authored-by: Debasish Biswas <debasishbsws.abc@gmail.com>

src/test/java/com/thealgorithms/sorts/InsertionSortTest.java

@@ -0,0 +1,114 @@
+package com.thealgorithms.sorts;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.function.Function;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class InsertionSortTest {
+    private InsertionSort insertionSort;
+
+    @BeforeEach
+    void setUp() {
+        insertionSort = new InsertionSort();
+    }
+
+    @Test
+    void insertionSortSortEmptyArrayShouldPass() {
+        testEmptyArray(insertionSort::sort);
+        testEmptyArray(insertionSort::sentinelSort);
+    }
+
+    private void testEmptyArray(Function<Integer[], Integer[]> sortAlgorithm) {
+        Integer[] array = {};
+        Integer[] sorted = sortAlgorithm.apply(array);
+        Integer[] expected = {};
+        assertArrayEquals(expected, sorted);
+        assertTrue(SortUtils.isSorted(sorted));
+    }
+
+    @Test
+    void insertionSortClassicalSortSingleValueArrayShouldPass() {
+        testSingleValue(insertionSort::sort);
+        testSingleValue(insertionSort::sentinelSort);
+    }
+
+    private void testSingleValue(Function<Integer[], Integer[]> sortAlgorithm) {
+        Integer[] array = {7};
+        Integer[] sorted = sortAlgorithm.apply(array);
+        Integer[] expected = {7};
+        assertArrayEquals(expected, sorted);
+        assertTrue(SortUtils.isSorted(sorted));
+    }
+
+    @Test
+    void insertionSortClassicalWithIntegerArrayShouldPass() {
+        testIntegerArray(insertionSort::sort);
+        testIntegerArray(insertionSort::sentinelSort);
+    }
+
+    private void testIntegerArray(Function<Integer[], Integer[]> sortAlgorithm) {
+        Integer[] array = {49, 4, 36, 9, 144, 1};
+        Integer[] sorted = sortAlgorithm.apply(array);
+        Integer[] expected = {1, 4, 9, 36, 49, 144};
+        assertArrayEquals(expected, sorted);
+        assertTrue(SortUtils.isSorted(sorted));
+    }
+
+    @Test
+    void insertionSortClassicalForArrayWithNegativeValuesShouldPass() {
+        testWithNegativeValues(insertionSort::sort);
+        testWithNegativeValues(insertionSort::sentinelSort);
+    }
+
+    private void testWithNegativeValues(Function<Integer[], Integer[]> sortAlgorithm) {
+        Integer[] array = {49, -36, -144, -49, 1, 9};
+        Integer[] sorted = sortAlgorithm.apply(array);
+        Integer[] expected = {-144, -49, -36, 1, 9, 49};
+        assertArrayEquals(expected, sorted);
+        assertTrue(SortUtils.isSorted(sorted));
+    }
+
+    @Test
+    void insertionSortClassicalForArrayWithDuplicateValuesShouldPass() {
+        testWithDuplicates(insertionSort::sort);
+        testWithDuplicates(insertionSort::sentinelSort);
+    }
+
+    private void testWithDuplicates(Function<Integer[], Integer[]> sortAlgorithm) {
+        Integer[] array = {36, 1, 49, 1, 4, 9};
+        Integer[] sorted = sortAlgorithm.apply(array);
+        Integer[] expected = {1, 1, 4, 9, 36, 49};
+        assertArrayEquals(expected, sorted);
+        assertTrue(SortUtils.isSorted(sorted));
+    }
+
+    @Test
+    void insertionSortClassicalWithStringArrayShouldPass() {
+        testWithStringArray(insertionSort::sort);
+        testWithStringArray(insertionSort::sentinelSort);
+    }
+
+    private void testWithStringArray(Function<String[], String[]> sortAlgorithm) {
+        String[] array = {"c", "a", "e", "b", "d"};
+        String[] sorted = sortAlgorithm.apply(array);
+        String[] expected = {"a", "b", "c", "d", "e"};
+        assertArrayEquals(expected, sorted);
+        assertTrue(SortUtils.isSorted(sorted));
+    }
+
+    @Test
+    void insertionSortClassicalWithRandomArrayPass() {
+        testWithRandomArray(insertionSort::sort);
+        testWithRandomArray(insertionSort::sentinelSort);
+    }
+
+    private void testWithRandomArray(Function<Double[], Double[]> sortAlgorithm) {
+        int randomSize = (int) (SortUtilsRandomGenerator.generateDouble() * 10_000);
+        Double[] array = SortUtilsRandomGenerator.generateArray(randomSize);
+        Double[] sorted = sortAlgorithm.apply(array);
+        assertTrue(SortUtils.isSorted(sorted));
+    }
+}

src/test/java/com/thealgorithms/sorts/SortUtilsRandomGeneratorTest.java

@@ -0,0 +1,31 @@
+package com.thealgorithms.sorts;
+
+import org.junit.jupiter.api.RepeatedTest;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class SortUtilsRandomGeneratorTest {
+
+    @RepeatedTest(1000)
+    void generateArray() {
+        int size = 1_000;
+        Double[] doubles = SortUtilsRandomGenerator.generateArray(size);
+        assertThat(doubles).hasSize(size);
+        assertThat(doubles).doesNotContainNull();
+    }
+
+    @Test
+    void generateArrayEmpty() {
+        int size = 0;
+        Double[] doubles = SortUtilsRandomGenerator.generateArray(size);
+        assertThat(doubles).hasSize(size);
+    }
+
+    @RepeatedTest(1000)
+    void generateDouble() {
+        Double randomDouble = SortUtilsRandomGenerator.generateDouble();
+        assertThat(randomDouble).isBetween(0.0, 1.0);
+        assertThat(randomDouble).isNotEqualTo(1.0);
+    }
+}

src/test/java/com/thealgorithms/sorts/SortUtilsTest.java

@@ -0,0 +1,44 @@
+package com.thealgorithms.sorts;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class SortUtilsTest {
+
+    @Test
+    void isSortedEmptyArray() {
+        Double[] emptyArray = {};
+        assertTrue(SortUtils.isSorted(emptyArray));
+    }
+
+    @Test
+    void isSortedWithSingleElement() {
+        Double[] singleElementArray = {1.0};
+        assertTrue(SortUtils.isSorted(singleElementArray));
+    }
+
+    @Test
+    void isSortedTrue() {
+        Integer[] array = {1, 1, 2, 3, 5, 8, 11};
+        assertTrue(SortUtils.isSorted(array));
+
+        Integer[] identicalArray = {1, 1, 1, 1, 1};
+        assertTrue(SortUtils.isSorted(identicalArray));
+
+        Double[] doubles = {-15.123, -15.111, 0.0, 0.12, 0.15};
+        assertTrue(SortUtils.isSorted(doubles));
+    }
+
+    @Test
+    void isSortedFalse() {
+        Double[] array = {1.0, 3.0, -0.15};
+        assertFalse(SortUtils.isSorted(array));
+
+        Integer[] array2 = {14, 15, 16, 1};
+        assertFalse(SortUtils.isSorted(array2));
+
+        Integer[] array3 = {5, 4, 3, 2, 1};
+        assertFalse(SortUtils.isSorted(array3));
+    }
+}