#17 insertion_quicksort

Author: wojtask

src/book/chapter7/section4.py

@@ -0,0 +1,28 @@
+from book.chapter7.section1 import partition
+from book.data_structures import Array
+from book.data_structures import CT
+from util import range_of
+
+
+def insertion_quicksort(A: Array[CT], p: int, r: int, k: int) -> None:
+    """Sorts an array using quicksort, if the array size exceeds a given threshold, and using insertion sort otherwise.
+
+    Args:
+        A: an Array containing the values to be sorted
+        p: the lower index of the subarray to sort
+        r: the upper index of the subarray to sort
+        k: the threshold of the subarray size below which the subarray is to be sorted using insertion sort
+    """
+    if p < r:
+        if r - p + 1 >= k:
+            q = partition(A, p, r)
+            insertion_quicksort(A, p, q - 1, k)
+            insertion_quicksort(A, q + 1, r, k)
+        else:
+            for i in range_of(p + 1, to=r):
+                key = A[i]
+                j = i - 1
+                while j > 0 and A[j] > key:
+                    A[j + 1] = A[j]
+                    j -= 1
+                A[j + 1] = key

test/test_book/test_chapter7.py

@@ -5,6 +5,7 @@
 
 from book.chapter7.section1 import quicksort
 from book.chapter7.section3 import randomized_quicksort
+from book.chapter7.section4 import insertion_quicksort
 from test_case import ClrsTestCase
 from test_util import create_array
 
@@ -32,3 +33,15 @@ def test_randomized_quicksort(self, data):
 
         self.assertArraySorted(A, end=n)
         self.assertArrayPermuted(A, elements, end=n)
+
+    @given(st.data())
+    def test_insertion_quicksort(self, data):
+        elements = data.draw(lists(integers(), min_size=1))
+        A = create_array(elements)
+        n = len(elements)
+        k = data.draw(integers(min_value=1, max_value=n))
+
+        insertion_quicksort(A, 1, n, k)
+
+        self.assertArraySorted(A, end=n)
+        self.assertArrayPermuted(A, elements, end=n)