From 2d7ab40c150a9aded09a9845635b98ffed71bfb5 Mon Sep 17 00:00:00 2001
From: Bence Lakos <bence.lakos@z-consulting.eu>
Date: Mon, 23 Mar 2020 12:45:05 +0100
Subject: [PATCH] Implement iterative binary search

---
 .../com/search/IterativeBinarySearch.java     | 38 +++++++++++++++++++
 .../com/search/IterativeBinarySearchTest.java | 26 +++++++++++++
 2 files changed, 64 insertions(+)
 create mode 100644 src/main/java/com/search/IterativeBinarySearch.java
 create mode 100644 src/test/java/com/search/IterativeBinarySearchTest.java

diff --git a/src/main/java/com/search/IterativeBinarySearch.java b/src/main/java/com/search/IterativeBinarySearch.java
new file mode 100644
index 000000000000..17d88808ef58
--- /dev/null
+++ b/src/main/java/com/search/IterativeBinarySearch.java
@@ -0,0 +1,38 @@
+package com.search;
+
+/**
+ * Binary search is an algorithm which finds the position of a target value within a sorted array
+ * <p>
+ * Worst-case performance	O(log n)
+ * Best-case performance	O(1)
+ * Average performance	O(log n)
+ * Worst-case space complexity	O(1)
+ */
+public final class IterativeBinarySearch {
+
+    /**
+     * @param array a sorted array
+     * @param key   the key to search in array
+     * @return the index of key in the array or -1 if not found
+     */
+    public static <T extends Comparable<T>> int find(T[] array, T key) {
+        int left = 0;
+        int right = array.length - 1;
+
+        while (left <= right) {
+            int middle = (left + right) / 2;
+            int compareTo = key.compareTo(array[middle]);
+
+            if (compareTo == 0) {
+                return middle;
+            } else if (compareTo < 0) {
+                right = --middle;
+            } else {
+                left = ++middle;
+            }
+        }
+
+        return -1;
+    }
+
+}
diff --git a/src/test/java/com/search/IterativeBinarySearchTest.java b/src/test/java/com/search/IterativeBinarySearchTest.java
new file mode 100644
index 000000000000..c434de9832cc
--- /dev/null
+++ b/src/test/java/com/search/IterativeBinarySearchTest.java
@@ -0,0 +1,26 @@
+package com.search;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class IterativeBinarySearchTest {
+
+    @Test
+    void testIterativeBinarySearch() {
+        Integer[] arr1 = {1, 2, 3, 5, 8, 13, 21, 34, 55};
+        Assertions.assertEquals(2, IterativeBinarySearch.find(arr1, 3), "Incorrect index");
+        Assertions.assertEquals(0, IterativeBinarySearch.find(arr1, 1), "Incorrect index");
+        Assertions.assertEquals(8, IterativeBinarySearch.find(arr1, 55), "Incorrect index");
+        Assertions.assertEquals(-1, IterativeBinarySearch.find(arr1, -2), "Incorrect index");
+        Assertions.assertEquals(-1, IterativeBinarySearch.find(arr1, 4), "Incorrect index");
+
+        String[] arr2 = {"A", "B", "C", "D"};
+        Assertions.assertEquals(2, IterativeBinarySearch.find(arr2, "C"), "Incorrect index");
+        Assertions.assertEquals(1, IterativeBinarySearch.find(arr2, "B"), "Incorrect index");
+        Assertions.assertEquals(-1, IterativeBinarySearch.find(arr2, "F"), "Incorrect index");
+
+        String[] arr3 = {};
+        Assertions.assertEquals(-1, IterativeBinarySearch.find(arr3, ""), "Incorrect index");
+    }
+
+}