Create flashsort.py

sorts/flashsort.py

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+"""
+This is a Python implementation of the flashsort algorithm.
+
+For doctests run the following command:
+python3 -m doctest -v flashsort.py
+
+For manual testing run:
+python3 flashsort.py
+"""
+
+
+def flash_sort(collection: list) -> list:
+    """A pure Python implementation of the flash sort algorithm.
+
+    :param collection: a mutable collection of comparable items in any order
+    :return: the same collection in ascending order
+
+    Examples:
+    >>> flash_sort([0, 5, 3, 2, 2])
+    [0, 2, 2, 3, 5]
+    >>> flash_sort([])
+    []
+    >>> flash_sort([-2, 5, 0, -45])
+    [-45, -2, 0, 5]
+    >>> collections = ([], [0, 5, 3, 2, 2], [-2, 5, 0, -45])
+    >>> all(sorted(collection) == flash_sort(collection) for collection in collections)
+    True
+    """
+
+    n = len(collection)
+    if n < 2:
+        return collection
+
+    max_value = max(collection)
+    min_value = min(collection)
+
+    m = int(n / 2)
+    L = [0] * m
+    if max_value == min_value:
+        return collection
+
+    for value in collection:
+        class_index = int(m * (value - min_value) / (max_value - min_value))
+        if class_index >= m:
+            class_index = m - 1
+        L[class_index] += 1
+
+    for i in range(1, m):
+        L[i] += L[i - 1]
+
+    output = [0] * n
+    for i in range(n - 1, -1, -1):
+        value = collection[i]
+        class_index = int(m * (value - min_value) / (max_value - min_value))
+        if class_index >= m:
+            class_index = m - 1
+        output[L[class_index] - 1] = value
+        L[class_index] -= 1
+    for i in range(n):
+        collection[i] = output[i]
+
+    return collection
+
+
+if __name__ == "__main__":
+    user_input = input("Enter numbers separated by a comma:\n").strip()
+    unsorted = [int(item) for item in user_input.split(",")]
+    print(flash_sort(unsorted))