Added Binary Search

Author: OmkarPathak

pygorithm/searching/binary_search.py

@@ -0,0 +1,38 @@
+# Author: OMKAR PATHAK
+# Created On: 1st August 2017
+
+# Best O(1); Average O(logn); Worst O(logn)
+
+def search(List, target):
+    '''This function performs a binary search on a sorted list and returns the position if successful else returns -1'''
+    left = 0                # First position of the list
+    right = len(List) - 1   # Last position of the list
+
+    try:
+        while left <= right:    # you can also write while True condition
+            mid = (left + right) // 2
+            if target == List[mid]:
+                return mid
+            elif target < List[mid]:
+                right =  mid - 1
+            else:
+                left = mid + 1
+        return -1
+    except TypeError:
+        return -1
+
+
+# time complexities
+def bestcase_complexity():
+    return 'O(1)'
+
+def averagecase_complexity():
+    return 'O(logn)'
+
+def worstcase_complexity():
+    return 'O(logn)'
+
+# easily retrieve the source code of the sort function
+def get_code():
+    import inspect
+    return inspect.getsource(search)