added exponential searching algo

searching_algo/exponentialSearch.py

@@ -0,0 +1,33 @@
+def search(arr, l, r, x):
+	if r >= l:
+		m = (l+r)/2
+		if arr[m] == x:
+			return m
+
+		if arr[m] > x:
+			return search(arr, l, m-1, x)
+
+		else:
+			return search(arr, m, r, x)
+
+	return -1
+
+def exponentialSearch(arr, n, x):
+
+	if arr[0] == x:
+		return 0
+
+	i = 1
+	while i<n and arr[i] <=x:
+		i = i*2
+
+	return search(arr, i/2, min(n, i), x)
+
+arr = [2, 3, 4, 7, 10, 40] 
+n = len(arr) 
+x = 10
+r = exponentialSearch(arr, n, x) 
+if r == -1: 
+    print "Element not found"
+else: 
+    print "Element is present at index %d" %(r)