diff --git a/src/main/java/com/search/TernarySearch.java b/src/main/java/com/search/TernarySearch.java new file mode 100644 index 00000000..e5ab1c8c --- /dev/null +++ b/src/main/java/com/search/TernarySearch.java @@ -0,0 +1,57 @@ +package com.search; + +/** + * A ternary search algorithm is a technique in computer science for finding the minimum or maximum of a unimodal function + * The algorithm determines either that the minimum or maximum cannot be in the first third of the domain + * or that it cannot be in the last third of the domain, then repeats on the remaining third. + *

+ * Worst-case performance Θ(log3(N)) + * Best-case performance O(1) + * Average performance Θ(log3(N)) + * Worst-case space complexity O(1) + */ +public final class TernarySearch { + + /** + * @param arr The **Sorted** array in which we will search the element. + * @param value The value that we want to search for. + * @return The index of the element if found. + * Else returns -1. + */ + public static > int find(T[] arr, T value) { + return search(arr, value, 0, arr.length - 1); + } + + /** + * @param arr The **Sorted** array in which we will search the element. + * @param key The value that we want to search for. + * @param start The starting index from which we will start Searching. + * @param end The ending index till which we will Search. + * @return Returns the index of the Element if found. + * Else returns -1. + */ + private static > int search(T[] arr, T key, int start, int end) { + if (start > end) { + return -1; + } + + int mid1 = start + (end - start) / 3; + int mid2 = start + 2 * (end - start) / 3; + + if (key.compareTo(arr[mid1]) == 0) { + return mid1; + } else if (key.compareTo(arr[mid2]) == 0) { + return mid2; + } + else if (key.compareTo(arr[mid1]) < 0) { + return search(arr, key, start, --mid1); + } + else if (key.compareTo(arr[mid2]) > 0) { + return search(arr, key, ++mid2, end); + } + else { + return search(arr, key, mid1, mid2); + } + } + +} diff --git a/src/test/java/com/search/TernarySearchTest.java b/src/test/java/com/search/TernarySearchTest.java new file mode 100644 index 00000000..e13895c6 --- /dev/null +++ b/src/test/java/com/search/TernarySearchTest.java @@ -0,0 +1,26 @@ +package com.search; + +import org.junit.jupiter.api.Assertions; +import org.junit.jupiter.api.Test; + +public class TernarySearchTest { + + @Test + void testTernarySearch() { + Integer[] arr1 = {1, 2, 3, 5, 8, 13, 21, 34, 55}; + Assertions.assertEquals(2, TernarySearch.find(arr1, 3), "Incorrect index"); + Assertions.assertEquals(0, TernarySearch.find(arr1, 1), "Incorrect index"); + Assertions.assertEquals(8, TernarySearch.find(arr1, 55), "Incorrect index"); + Assertions.assertEquals(-1, TernarySearch.find(arr1, -2), "Incorrect index"); + Assertions.assertEquals(-1, TernarySearch.find(arr1, 4), "Incorrect index"); + + String[] arr2 = {"A", "B", "C", "D"}; + Assertions.assertEquals(2, TernarySearch.find(arr2, "C"), "Incorrect index"); + Assertions.assertEquals(1, TernarySearch.find(arr2, "B"), "Incorrect index"); + Assertions.assertEquals(-1, TernarySearch.find(arr2, "F"), "Incorrect index"); + + String[] arr3 = {}; + Assertions.assertEquals(-1, TernarySearch.find(arr3, ""), "Incorrect index"); + } + +}