Implement iterative ternary search

src/main/java/com/search/IterativeTernarySearch.java

@@ -0,0 +1,51 @@
+package com.search;
+
+/**
+ * A iterative version of a ternary search algorithm
+ * This is better way to implement the ternary search, because a recursive version adds some overhead to a stack.
+ * But in java the compile can transform the recursive version to iterative implicitly,
+ * so there are no much differences between these two algorithms
+ * <p>
+ * 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 IterativeTernarySearch {
+
+    /**
+     * @param array 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 <T extends Comparable<T>> int find(T[] array, T value) {
+        int left = 0;
+        int right = array.length - 1;
+
+        while (right > left) {
+            int leftCompareTo = array[left].compareTo(value);
+            int rightCompareTo = array[right].compareTo(value);
+
+            if (leftCompareTo == 0) {
+                return left;
+            }
+
+            if (rightCompareTo == 0) {
+                return right;
+            }
+
+            int leftThird = left + (right - left) / 3 + 1;
+            int rightThird = right - (right - left) / 3 - 1;
+
+            if (array[leftThird].compareTo(value) <= 0) {
+                left = leftThird;
+            } else {
+                right = rightThird;
+            }
+        }
+
+        return -1;
+    }
+
+}

src/test/java/com/search/IterativeTernarySearchTest.java

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+package com.search;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class IterativeTernarySearchTest {
+
+    @Test
+    void testIterativeTernarySearch() {
+        Integer[] arr1 = {1, 2, 3, 5, 8, 13, 21, 34, 55};
+        Assertions.assertEquals(2, IterativeTernarySearch.find(arr1, 3), "Incorrect index");
+        Assertions.assertEquals(0, IterativeTernarySearch.find(arr1, 1), "Incorrect index");
+        Assertions.assertEquals(8, IterativeTernarySearch.find(arr1, 55), "Incorrect index");
+        Assertions.assertEquals(-1, IterativeTernarySearch.find(arr1, -2), "Incorrect index");
+        Assertions.assertEquals(-1, IterativeTernarySearch.find(arr1, 4), "Incorrect index");
+
+        String[] arr2 = {"A", "B", "C", "D"};
+        Assertions.assertEquals(2, IterativeTernarySearch.find(arr2, "C"), "Incorrect index");
+        Assertions.assertEquals(1, IterativeTernarySearch.find(arr2, "B"), "Incorrect index");
+        Assertions.assertEquals(-1, IterativeTernarySearch.find(arr2, "F"), "Incorrect index");
+
+        String[] arr3 = {};
+        Assertions.assertEquals(-1, IterativeTernarySearch.find(arr3, ""), "Incorrect index");
+    }
+
+}