#17 stooge_sort

Author: wojtask

src/book/chapter7/problem4.py

@@ -0,0 +1,22 @@
+from book.data_structures import Array
+from book.data_structures import CT
+
+
+def stooge_sort(A: Array[CT], p: int, r: int) -> None:
+    """Sorts an array using stooge sort.
+
+    Implements:
+        Stooge-Sort
+
+    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
+    """
+    if A[p] > A[r]:
+        A[p], A[r] = A[r], A[p]
+    if p + 1 < r:
+        k = (r - p + 1) // 3
+        stooge_sort(A, p, r - k)
+        stooge_sort(A, p + k, r)
+        stooge_sort(A, p, r - k)

test/test_book/test_chapter7.py

@@ -3,6 +3,7 @@
 from hypothesis.strategies import integers
 from hypothesis.strategies import lists
 
+from book.chapter7.problem4 import stooge_sort
 from book.chapter7.section1 import quicksort
 from book.chapter7.section3 import randomized_quicksort
 from book.chapter7.section4 import insertion_quicksort
@@ -61,3 +62,14 @@ def test_median_of_3_partition(self, data):
         for i in range_of(actual_pivot_index + 1, to=n):
             self.assertGreaterEqual(A[i], A[actual_pivot_index])
         self.assertArrayPermuted(A, elements, end=n)
+
+    @given(st.data())
+    def test_stooge_sort(self, data):
+        elements = data.draw(lists(integers(), min_size=1))
+        A = create_array(elements)
+        n = len(elements)
+
+        stooge_sort(A, 1, n)
+
+        self.assertArraySorted(A, end=n)
+        self.assertArrayPermuted(A, elements, end=n)