Added rotated binary search div-bargali#550

Added rotated binary search

Author: div-bargali

Java/Algorithms/Searching-Algorithms/BinarySearch/rotated_binary_search.java

@@ -0,0 +1,57 @@
+public class rotated_binary_search{
+
+ static int binarySearch(int arr[], int low, int high, int key) 
+ { 
+ if (high < low) 
+ return -1; 
+ 
+ /* low + (high - low)/2; */
+ int mid = (low + high) / 2; 
+ if (key == arr[mid]) 
+ return mid; 
+ if (key > arr[mid]) 
+ return binarySearch(arr, (mid + 1), high, key); 
+ return binarySearch(arr, low, (mid - 1), key); 
+ } 
+
+ static int pivotedBinarySearch(int arr[], int n, int key) 
+ { 
+ int pivot = findPivot(arr, 0, n - 1); 
+ if (pivot == -1) 
+ return binarySearch(arr, 0, n - 1, key); 
+ 
+ 
+ if (arr[pivot] == key) 
+ return pivot; 
+ if (arr[0] <= key) 
+ return binarySearch(arr, 0, pivot - 1, key); 
+ return binarySearch(arr, pivot + 1, n - 1, key); 
+ } 
+
+ static int findPivot(int arr[], int low, int high) 
+ { 
+ // base cases 
+ if (high < low) 
+ return -1; 
+ if (high == low) 
+ return low; 
+ 
+ /* low + (high - low)/2; */
+ int mid = (low + high) / 2; 
+ if (mid < high && arr[mid] > arr[mid + 1]) 
+ return mid; 
+ if (mid > low && arr[mid] < arr[mid - 1]) 
+ return (mid - 1); 
+ if (arr[low] >= arr[mid]) 
+ return findPivot(arr, low, mid - 1); 
+ return findPivot(arr, mid + 1, high); 
+ }
+
+ public static void main(String [] args){
+ int arr1[] = { 5, 6, 7, 8, 9, 10, 1, 2, 3 }; 
+ int n = arr1.length; 
+ int key = 3; 
+ System.out.println("Index of the element is : "
+ + pivotedBinarySearch(arr1, n, key)); 
+ }
+}