Optimize bubbe sort (#417)

* Optimize bubbe sort

- as after each step of 'outer-loop', one number reaches to its right position. Thus inner loop does not need to run for 'n' times in every cycle of 'outer-loop'.

* Followed PEP for PR #417

algorithms/sort/bubble_sort.py

@@ -20,10 +20,11 @@ def swap(i, j):
     iteration = 0
     if simulation:
         print("iteration",iteration,":",*arr)
-
+    x = -1
     while swapped:
         swapped = False
-        for i in range(1, n):
+        x = x + 1
+        for i in range(1, n-x):
             if arr[i - 1] > arr[i]:
                 swap(i - 1, i)
                 swapped = True