quicksort

src/sort/quick_sort.py

@@ -0,0 +1,22 @@
+import random
+
+def sort(array):
+    def get_partition(array, start_idx, end_idx):
+        pivot_idx = random.randint(start_idx, end_idx)
+        pivot = array[pivot_idx]
+        array[pivot_idx], array[end_idx] = array[end_idx], array[pivot_idx]
+        i = start_idx - 1
+        for j in range(start_idx, end_idx):
+            if array[j] <= pivot:
+                i += 1
+                array[i], array[j] = array[j], array[i]
+        array[i + 1], array[end_idx] = array[end_idx], array[i + 1]
+        return i + 1
+
+    def quick_sort(array, start_idx, end_idx):
+        if start_idx < end_idx:
+            partition = get_partition(array, start_idx, end_idx)
+            quick_sort(array, start_idx, partition - 1)
+            quick_sort(array, partition + 1, end_idx)
+
+    quick_sort(array, 0, len(array) - 1)

tst/sort/test_quick_sort.py

@@ -0,0 +1,34 @@
+from src.sort.quick_sort import sort
+
+class TestQuickSort:
+    def test_empty_sort(self):
+        array = []
+        sort(array)
+        assert array == []
+
+    def test_sorted_and_reverse_inputs(self):
+        sorted_array = [1, 2, 3, 4, 5]
+        reverse_array = list(reversed(sorted_array))
+        sort(sorted_array)
+        sort(reverse_array)
+        assert sorted_array == [1, 2, 3, 4, 5]
+        assert reverse_array == [1, 2, 3, 4, 5]
+
+    def test_duplicates_and_negatives(self):
+        array = [3, -1, 0, -1, 5, 3, 2]
+        sort(array)
+        assert array == [-1, -1, 0, 2, 3, 3, 5]
+
+    def test_random_pivot_usage(self, monkeypatch):
+        calls = []
+
+        def fake_randint(start_idx, end_idx):
+            calls.append((start_idx, end_idx))
+            return start_idx  # pick first element to force swaps with pivot
+
+        monkeypatch.setattr("src.sort.quick_sort.random.randint", fake_randint)
+        array = [10, 5, 8, 3, 2]
+        sort(array)
+        assert array == [2, 3, 5, 8, 10]
+        assert calls[0] == (0, 4)
+        assert all(start <= end for start, end in calls)