add ternarysearch algo

src/algo/sortingandsearching/ternarysearch.java

@@ -0,0 +1,91 @@
+class Geeks { 
+
+    // Function to perform Ternary Search 
+    static int ternarySearch(int l, int r, int key, int ar[]) 
+
+    { 
+        while (r >= l) { 
+
+            // Find the mid1  mid2 
+            int mid1 = l + (r - l) / 3; 
+            int mid2 = r - (r - l) / 3; 
+
+            // Check if key is present at any mid 
+            if (ar[mid1] == key) { 
+                return mid1; 
+            } 
+            if (ar[mid2] == key) { 
+                return mid2; 
+            } 
+
+            // Since key is not present at mid, 
+            // check in which region it is present 
+            // then repeat the Search operation 
+            // in that region 
+
+            if (key < ar[mid1]) { 
+
+                // The key lies in between l and mid1 
+                r = mid1 - 1; 
+            } 
+            else if (key > ar[mid2]) { 
+
+                // The key lies in between mid2 and r 
+                l = mid2 + 1; 
+            } 
+            else { 
+
+                // The key lies in between mid1 and mid2 
+                l = mid1 + 1; 
+                r = mid2 - 1; 
+            } 
+        } 
+
+        // Key not found 
+        return -1; 
+    } 
+
+    // Driver code 
+    public static void main(String args[]) 
+    { 
+        int l, r, p, key; 
+
+        // Get the array 
+        // Sort the array if not sorted 
+        int ar[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; 
+
+        // Starting index 
+        l = 0; 
+
+        // length of array 
+        r = 9; 
+
+        // Checking for 5 
+
+        // Key to be searched in the array 
+        key = 5; 
+
+        // Search the key using ternarySearch 
+        p = ternarySearch(l, r, key, ar); 
+
+        // Print the result 
+        System.out.println("Index of " + key + " is " + p); 
+
+        // Checking for 50 
+
+        // Key to be searched in the array 
+        key = 50; 
+
+        // Search the key using ternarySearch 
+        p = ternarySearch(l, r, key, ar); 
+
+        // Print the result 
+        System.out.println("Index of " + key + " is " + p); 
+    } 
+} 
+Output:
+Index of 5 is 4
+Index of 50 is -1
+Time Complexity: O(\log _{3} n), where n is the size of the array.
+
+Uses: In finding the maximum or minimum of a unimodal function.