update quicksort.py

Author: Zidong Zhang

Python_utils Python_utils.txt

@@ -1,4 +1,8 @@
 1) List
+  len(lst)
+	lst[-1]
+  lst1 + lst2
+  cmp(list1, list2)
 	sorted(lst)
 	lst.sort()
 	lst.append(e)
@@ -21,9 +25,9 @@
 	print ''.join(['h','i'])
 	print ord('a')
 	print '1 2'.split()
-   
+
  4) if __name__ == '__main__':
- 5) 
+ 5)
  6) for i in range(len(lst)-1,-1,-1):
  7) {char:[] for char in Set}
  8) min(lst, key=foo)
@@ -48,4 +52,4 @@ except:
 # 17) from collections import deque
 	  queue = deque([1,2,3])
 	  queue.append(4)
-	  queue.popleft() # FIFO
+	  queue.popleft() # FIFO

Util/quicksort.py

@@ -1,24 +1,66 @@
+import unittest
+
+
 # sort a list of numbers
 def quicksort(lst):
-	if len(lst)<=1:
-	    return lst
-	    
-	pivot = lst[0]
-	left,right = partition(lst[1:],pivot)
-	return quicksort(left) + [pivot] + quicksort(right)
+    if len(lst) <= 1:
+        return lst
+
+    pivot = lst[0]
+    left, right = partition(lst[1:], pivot)
+    return quicksort(left) + [pivot] + quicksort(right)
+
 
 # lenght of lst is at least 1
-def partition(lst,pivot):
+def partition(lst, pivot):
     left = 0
     right = 0
     while right != len(lst):
         if lst[right] < pivot:
-            lst[left],lst[right] = lst[right],lst[left]
+            lst[left], lst[right] = lst[right], lst[left]
             left += 1
         right += 1
-    return lst[:left],lst[left:]
+    return lst[:left], lst[left:]
+
+
+# the orginal lst remains unchanged after calling this method
+def lomuto_quicksort_not_in_place(lst):
+    if len(lst) <= 1:
+        return lst
+    pivot, lst1, lst2 = lst[-1], [], []
+    for e in lst[:-1]:
+        if e <= pivot:
+            lst1.append(e)
+        else:
+            lst2.append(e)
+    sorted_lst1 = lomuto_quicksort_not_in_place(lst1)
+    sorted_lst2 = lomuto_quicksort_not_in_place(lst2)
+    return sorted_lst1 + [pivot] + sorted_lst2
+
+
+class TestQuicksort(unittest.TestCase):
+    # return a list of tuples (lst_unsorted, expected)
+    def data_provider(self):
+        return [
+            ([], []),
+            ([1], [1]),
+            ([1, 2], [1, 2]),
+            ([2, 1], [1, 2]),
+            ([3, 2, 1], [1, 2, 3]),
+            ([1, 3, 2, 1, 2], [1, 1, 2, 2, 3]),
+            ([6, 0, 8, 8, 8, 6, 7, 3, 3, 6], [0, 3, 3, 6, 6, 6, 7, 8, 8, 8]),
+        ]
+
+    # Date: 2015
+    def test_quicksort(self):
+        for lst_unsorted, expected in self.data_provider():
+            self.assertEqual(quicksort(lst_unsorted), expected)
+
+    # Date: Nov 11, 2018
+    def test_lomuto_quicksort_not_in_place(self):
+        for lst_unsorted, expected in self.data_provider():
+            self.assertEqual(lomuto_quicksort_not_in_place(lst_unsorted), expected)
 
 
 if __name__ == '__main__':
-    print quicksort([6,9,2,9,10,6])
-    print quicksort([2,1])
+    unittest.main()