Add: SentinelBinarySearch algorithm with tests

src/main/java/com/thealgorithms/searches/SentinelBinarySearch.java

@@ -0,0 +1,46 @@
+package com.thealgorithms.searches;
+
+/**
+* Sentinel Binary Search algorithm implementation
+*
+* Sentinel Binary Search is a variation of Binary Search that
+* reduces the number of comparisons by placing a sentinel value 
+* at the end of the array, eliminating the need to check array 
+* bounds on every step.
+*
+* Worst case: O(logn)
+* Best case: O(1)
+*
+* <a href="https://en.wikipedia.org/wiki/Linear_search#With_a_sentinel">Wiki</a>
+*/
+public class SentinelBinarySearch {
+    /**
+     * Finds the index of a target value in a sorted array.
+     * 
+     * @param arr the sorted array to search
+     * @param target the value to find 
+     * @return the index of target if found, otherwise -1
+     */
+    public int find(int[] arr, int target){
+        int n = arr.length;
+
+        if(n == 0){
+            return -1;
+        }
+
+        int last = arr[n-1];
+        arr[n-1] = target;
+
+        int i = 0;
+        while(arr[i] != target){
+            i++;
+        }
+
+        arr[n-1] = last;
+
+        if (i<n-1 || last == target){
+            return i;
+        }
+        return -1;
+    }
+}

src/test/java/com/thealgorithms/searches/SentinelBinarySearchTest.java

@@ -0,0 +1,38 @@
+package com.thealgorithms.searches;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class SentinelBinarySearchTest {
+    private final SentinelBinarySearch search = new SentinelBinarySearch();
+
+    @Test
+    void testElementFound(){
+        int[] arr = {1, 3, 5, 7, 9};
+        assertEquals(2, search.find(arr, 5));
+    }
+
+    @Test
+    void testElementNotFound(){
+        int[] arr = {1, 3, 5, 7, 9};
+        assertEquals(-1, search.find(arr, 4));
+    }
+
+    @Test
+    void testFirstElement() {
+        int[] arr = {1, 3, 5, 7, 9};
+        assertEquals(0, search.find(arr, 1));
+    }
+
+    @Test
+    void testLastElement() {
+        int[] arr = {1, 3, 5, 7, 9};
+        assertEquals(4, search.find(arr, 9));
+    }
+
+    @Test
+    void testEmptyArray() {
+        int[] arr = {};
+        assertEquals(-1, search.find(arr, 5));
+    }
+}