TernarySearchTest.java

package com.thealgorithms.searches;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

import org.junit.jupiter.api.Test;

class TernarySearchTest {

    @Test
    void testFindElementInSortedArray() {
        Integer[] arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        TernarySearch search = new TernarySearch();

        int index = search.find(arr, 5);

        assertEquals(4, index, "Should find the element 5 at index 4");
    }

    @Test
    void testElementNotFound() {
        Integer[] arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        TernarySearch search = new TernarySearch();

        int index = search.find(arr, 11);

        assertEquals(-1, index, "Should return -1 for element 11 which is not present");
    }

    @Test
    void testFindFirstElement() {
        Integer[] arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        TernarySearch search = new TernarySearch();

        int index = search.find(arr, 1);

        assertEquals(0, index, "Should find the first element 1 at index 0");
    }

    @Test
    void testFindLastElement() {
        Integer[] arr = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        TernarySearch search = new TernarySearch();

        int index = search.find(arr, 10);

        assertEquals(9, index, "Should find the last element 10 at index 9");
    }

    @Test
    void testFindInLargeArray() {
        Integer[] arr = new Integer[1000];
        for (int i = 0; i < 1000; i++) {
            arr[i] = i + 1; // Array from 1 to 1000
        }
        TernarySearch search = new TernarySearch();

        int index = search.find(arr, 500);

        assertEquals(499, index, "Should find element 500 at index 499");
    }

    @Test
    void testNegativeNumbers() {
        Integer[] arr = {-10, -5, -3, -1, 0, 1, 3, 5, 7, 10};
        TernarySearch search = new TernarySearch();

        int index = search.find(arr, -3);

        assertEquals(2, index, "Should find the element -3 at index 2");
    }

    @Test
    void testEdgeCaseEmptyArray() {
        Integer[] arr = {};
        TernarySearch search = new TernarySearch();

        int index = search.find(arr, 5);

        assertEquals(-1, index, "Should return -1 for an empty array");
    }

    @Test
    void testNullArrayReturnsMinusOne() {
        TernarySearch search = new TernarySearch();
        assertEquals(-1, search.find(null, 5));
    }

    @Test
    void testNullKeyReturnsMinusOne() {
        Integer[] arr = {1, 2, 3, 4, 5};
        TernarySearch search = new TernarySearch();
        assertEquals(-1, search.find(arr, null));
    }

    @Test
    void testSingleElementPresent() {
        Integer[] arr = {42};
        TernarySearch search = new TernarySearch();
        assertEquals(0, search.find(arr, 42));
    }

    @Test
    void testSingleElementAbsent() {
        Integer[] arr = {42};
        TernarySearch search = new TernarySearch();
        assertEquals(-1, search.find(arr, 24));
    }

    @Test
    void testTwoElements() {
        Integer[] arr = {10, 20};
        TernarySearch search = new TernarySearch();
        assertEquals(0, search.find(arr, 10));
        assertEquals(1, search.find(arr, 20));
        assertEquals(-1, search.find(arr, 15));
    }

    @Test
    void testMiddlePartitionSearch() {
        Integer[] arr = {1, 3, 5, 7, 9, 11, 13, 15, 17, 19};
        TernarySearch search = new TernarySearch();
        assertEquals(3, search.find(arr, 7));
        assertEquals(4, search.find(arr, 9));
        assertEquals(5, search.find(arr, 11));
    }

    @Test
    void testDuplicateElements() {
        Integer[] arr = {1, 2, 2, 2, 3};
        TernarySearch search = new TernarySearch();
        int index = search.find(arr, 2);
        assertTrue(index >= 1 && index <= 3, "Index should be one of the occurrences of 2");
    }

    @Test
    void testGenericStrings() {
        String[] words = {"apple", "banana", "cherry", "date", "elderberry"};
        TernarySearch search = new TernarySearch();
        assertEquals(2, search.find(words, "cherry"));
        assertEquals(-1, search.find(words, "fig"));
    }
}