Create intro_sort.py

sorts/intro_sort.py

@@ -0,0 +1,103 @@
+"""
+Introspective Sort is hybrid sort (Quick Sort + Heap Sort + Insertion Sort)
+if the size of the list is under 16, use insertion sort
+"""
+import math
+import random
+
+
+def insertion_sort(array: list, start: int, end: int) -> list:
+    for i in range(start, end):
+        temp_index = i
+        temp_index_value = array[i]
+        while temp_index != start and temp_index_value < array[temp_index - 1]:
+            array[temp_index] = array[temp_index - 1]
+            temp_index -= 1
+        array[temp_index] = temp_index_value
+    return array
+
+
+def heapify(array: list, index: int, heap_size: int):  # Max Heap
+    largest = index
+    left_index = 2 * index + 1  # Left Node
+    right_index = 2 * index + 2  # Right Node
+
+    if left_index < heap_size and array[largest] < array[left_index]:
+        largest = left_index
+
+    if right_index < heap_size and array[largest] < array[right_index]:
+        largest = right_index
+
+    if largest != index:
+        array[index], array[largest] = array[largest], array[index]
+        heapify(array, largest, heap_size)
+
+
+def heap_sort(array: list) -> list:
+    n = len(array)
+
+    for i in range(n // 2, -1, -1):
+        heapify(array, n, i)
+
+    for i in range(n - 1, 0, -1):
+        array[i], array[0] = array[0], array[i]
+        heapify(array, 0, i)
+
+    return array
+
+
+def median_of_3(
+    array: list, first_index: int, middle_index: int, last_index: int
+) -> int:
+    if (array[first_index] > array[middle_index]) != (
+        array[first_index] > array[last_index]
+    ):
+        return array[first_index]
+    elif (array[middle_index] > array[first_index]) != (
+        array[middle_index] > array[last_index]
+    ):
+        return array[middle_index]
+    else:
+        return array[last_index]
+
+
+def partition(array: list, low: int, high: int, pivot: int) -> int:
+    i = low
+    j = high
+    while True:
+        while array[i] < pivot:
+            i += 1
+        j -= 1
+        while pivot < array[j]:
+            j -= 1
+        if i >= j:
+            return i
+        array[i], array[j] = array[j], array[i]
+        i += 1
+
+
+def sort(array: list):
+    max_depth = 2 * math.ceil(math.log2(len(array)))
+    size_threshold = 16
+    return intro_sort(array, 0, len(array), size_threshold, max_depth)
+
+
+def intro_sort(array: list, start: int, end: int, size_threshold: int, max_depth: int):
+    # if size > 16: heap sort or quick sort
+    while end - start > size_threshold:
+        if max_depth == 0:
+            return heap_sort(array)
+        max_depth -= 1
+        pivot = median_of_3(array, start, start + ((end - start) // 2) + 1, end)
+        p = partition(array, start, end, pivot)
+        intro_sort(array, p, end, size_threshold, max_depth)
+        end = p
+    return insertion_sort(array)
+
+
+if __name__ == "__main__":
+    array = []
+    for i in range(30):
+        array.append(random.randrange(100))
+
+    assert sort(array) == sorted(array)