Merge pull request #2 from csana004/csana004-patch-1

Update merge_sort.py

Author: csana004

sorts/merge_sort.py

@@ -1,274 +1,153 @@
 """
-For doctests, run the following command:
-python -m doctest -v merge_sort.py
-or
-python3 -m doctest -v merge_sort.py
+Merge Sort Algorithm
+====================
 
-For manual testing, run:
-python merge_sort.py
-"""
+This module implements the Merge Sort algorithm with three variations:
+1. Recursive Merge Sort
+2. Iterative Merge Sort
+3. Merge Insertion Sort
 
-from __future__ import annotations
-import itertools
-import doctest
-import sys
+Usage:
+    - Run this module directly for manual testing.
+    - Use doctests to verify correctness.
 
+Example:
+    python merge_sort.py
+"""
 
-def binary_search_insertion(sorted_list: list[int], item: int) -> list[int]:
-    """
-    Inserts an item into a sorted list while maintaining order.
+from typing import List
 
-    >>> binary_search_insertion([1, 2, 7, 9, 10], 4)
-    [1, 2, 4, 7, 9, 10]
+def merge_sort(arr: List[int]) -> List[int]:
     """
-    left = 0
-    right = len(sorted_list) - 1
-    while left <= right:
-        middle = (left + right) // 2
-        if left == right:
-            if sorted_list[middle] < item:
-                left = middle + 1
-            break
-        elif sorted_list[middle] < item:
-            left = middle + 1
-        else:
-            right = middle - 1
-    sorted_list.insert(left, item)
-    return sorted_list
+    Perform merge sort on a list of integers.
 
+    Args:
+        arr: A list of integers.
 
-def merge(left: list[list[int]], right: list[list[int]]) -> list[list[int]]:
-    """
-    Merges two sorted lists into a single sorted list.
+    Returns:
+        A sorted list of integers.
 
-    >>> merge([[1, 6], [9, 10]], [[2, 3], [4, 5], [7, 8]])
-    [[1, 6], [2, 3], [4, 5], [7, 8], [9, 10]]
+    Example:
+        >>> merge_sort([8, 3, 5, 6])
+        [3, 5, 6, 8]
     """
-    result = []
-    while left and right:
-        if left[0][0] < right[0][0]:
-            result.append(left.pop(0))
-        else:
-            result.append(right.pop(0))
-    return result + left + right
+    if len(arr) > 1:
+        mid = len(arr) // 2
+        left_half = arr[:mid]
+        right_half = arr[mid:]
 
+        merge_sort(left_half)
+        merge_sort(right_half)
 
-def sortlist_2d(list_2d: list[list[int]]) -> list[list[int]]:
-    """
-    Sorts a 2D list based on the first element of each sublist.
+        i = j = k = 0
 
-    >>> sortlist_2d([[9, 10], [1, 6], [7, 8], [2, 3], [4, 5]])
-    [[1, 6], [2, 3], [4, 5], [7, 8], [9, 10]]
-    """
-    length = len(list_2d)
-    if length <= 1:
-        return list_2d
-    middle = length // 2
-    return merge(sortlist_2d(list_2d[:middle]), sortlist_2d(list_2d[middle:]))
+        while i < len(left_half) and j < len(right_half):
+            if left_half[i] < right_half[j]:
+                arr[k] = left_half[i]
+                i += 1
+            else:
+                arr[k] = right_half[j]
+                j += 1
+            k += 1
 
+        while i < len(left_half):
+            arr[k] = left_half[i]
+            i += 1
+            k += 1
 
-def merge_insertion_sort(collection: list[int]) -> list[int]:
-    """Pure implementation of merge-insertion sort algorithm in Python
+        while j < len(right_half):
+            arr[k] = right_half[j]
+            j += 1
+            k += 1
 
-    :param collection: some mutable ordered collection with comparable items inside
-    :return: the same collection ordered by ascending
+    return arr
 
-    Examples:
-    >>> merge_insertion_sort([0, 5, 3, 2, 2])
-    [0, 2, 2, 3, 5]
+def iterative_merge_sort(arr: List[int]) -> List[int]:
+    """
+    Perform iterative merge sort on a list of integers.
 
-    >>> merge_insertion_sort([99])
-    [99]
+    Args:
+        arr: A list of integers.
 
-    >>> merge_insertion_sort([-2, -5, -45])
-    [-45, -5, -2]
+    Returns:
+        A sorted list of integers.
 
-    Testing with all permutations on range(0,5):
-    >>> import itertools
-    >>> permutations = list(itertools.permutations([0, 1, 2, 3, 4]))
-    >>> all(merge_insertion_sort(p) == [0, 1, 2, 3, 4] for p in permutations)
-    True
+    Example:
+        >>> iterative_merge_sort([8, 3, 5, 6])
+        [3, 5, 6, 8]
     """
+    if len(arr) <= 1:
+        return arr
 
-    if len(collection) <= 1:
-        return collection
+    width = 1
+    n = len(arr)
+    while width < n:
+        for i in range(0, n, 2 * width):
+            left = arr[i:i + width]
+            right = arr[i + width:i + 2 * width]
+            merged = merge(left, right)
+            arr[i:i + len(merged)] = merged
+        width *= 2
 
-    two_paired_list = []
-    has_last_odd_item = False
-    for i in range(0, len(collection), 2):
-        if i == len(collection) - 1:
-            has_last_odd_item = True
-        else:
-            if collection[i] < collection[i + 1]:
-                two_paired_list.append([collection[i], collection[i + 1]])
-            else:
-                two_paired_list.append([collection[i + 1], collection[i]])
-
-    sorted_list_2d = sortlist_2d(two_paired_list)
-    result = [i[0] for i in sorted_list_2d]
-    result.append(sorted_list_2d[-1][1])
-
-    if has_last_odd_item:
-        pivot = collection[-1]
-        result = binary_search_insertion(result, pivot)
-
-    is_last_odd_item_inserted_before_this_index = False
-    for i in range(len(sorted_list_2d) - 1):
-        if result[i] == collection[-1] and has_last_odd_item:
-            is_last_odd_item_inserted_before_this_index = True
-        pivot = sorted_list_2d[i][1]
-        if is_last_odd_item_inserted_before_this_index:
-            result = result[: i + 2] + binary_search_insertion(result[i + 2 :], pivot)
-        else:
-            result = result[: i + 1] + binary_search_insertion(result[i + 1 :], pivot)
+    return arr
 
-    return result
+def merge(left: List[int], right: List[int]) -> List[int]:
+    """
+    Merge two sorted lists into a single sorted list.
 
+    Args:
+        left: A sorted list of integers.
+        right: A sorted list of integers.
 
-def merge_iter(input_list: list[int], low: int, mid: int, high: int) -> list[int]:
-    """
-    Sorts the left-half and right-half individually then merges them into a result.
+    Returns:
+        A merged and sorted list of integers.
 
-    :param input_list: List to be sorted.
-    :param low: Starting index of the segment.
-    :param mid: Middle index to split the segment.
-    :param high: Ending index of the segment.
-    :return: Merged sorted list.
+    Example:
+        >>> merge([1, 3, 5], [2, 4, 6])
+        [1, 2, 3, 4, 5, 6]
     """
-    left = input_list[low : mid + 1]
-    right = input_list[mid + 1 : high + 1]
-    result = []
-
+    merged = []
     i = j = 0
+
     while i < len(left) and j < len(right):
-        if left[i] <= right[j]:
-            result.append(left[i])
+        if left[i] < right[j]:
+            merged.append(left[i])
             i += 1
         else:
-            result.append(right[j])
+            merged.append(right[j])
             j += 1
 
-    result.extend(left[i:])
-    result.extend(right[j:])
-
-    input_list[low : high + 1] = result
-    return input_list
-
-
-def iter_merge_sort(input_list: list[int]) -> list[int]:
-    """
-    Return a sorted copy of the input list using iterative merge sort.
-
-    >>> iter_merge_sort([5, 9, 8, 7, 1, 2, 7])
-    [1, 2, 5, 7, 7, 8, 9]
-    >>> iter_merge_sort([1])
-    [1]
-    >>> iter_merge_sort([2, 1])
-    [1, 2]
-    >>> iter_merge_sort([2, 1, 3])
-    [1, 2, 3]
-    >>> iter_merge_sort([4, 3, 2, 1])
-    [1, 2, 3, 4]
-    >>> iter_merge_sort([5, 4, 3, 2, 1])
-    [1, 2, 3, 4, 5]
-    >>> iter_merge_sort(['c', 'b', 'a'])
-    ['a', 'b', 'c']
-    >>> iter_merge_sort([0.3, 0.2, 0.1])
-    [0.1, 0.2, 0.3]
-    >>> iter_merge_sort(['dep', 'dang', 'trai'])
-    ['dang', 'dep', 'trai']
-    >>> iter_merge_sort([6])
-    [6]
-    >>> iter_merge_sort([])
-    []
-    >>> iter_merge_sort([-2, -9, -1, -4])
-    [-9, -4, -2, -1]
-    >>> iter_merge_sort([1.1, 1, 0.0, -1, -1.1])
-    [-1.1, -1, 0.0, 1, 1.1]
-    """
-    if not isinstance(input_list, list):
-        raise TypeError("Input must be a list")
-
-    n = len(input_list)
-    if n <= 1:
-        return input_list
+    merged.extend(left[i:])
+    merged.extend(right[j:])
 
-    width = 1
-    while width < n:
-        for i in range(0, n, 2 * width):
-            low = i
-            mid = min(i + width - 1, n - 1)
-            high = min(i + 2 * width - 1, n - 1)
-            if mid < high:
-                merge_iter(input_list, low, mid, high)
-        width *= 2
-
-    return input_list
+    return merged
 
-
-def merge_sort(collection: list[int]) -> list[int]:
+def merge_insertion_sort(arr: List[int]) -> List[int]:
     """
-    Sorts a list using the merge sort algorithm.
+    Perform merge insertion sort on a list of integers.
 
-    :param collection: A mutable ordered collection with comparable items.
-    :return: The same collection ordered in ascending order.
+    Args:
+        arr: A list of integers.
 
-    Time Complexity: O(n log n)
+    Returns:
+        A sorted list of integers.
 
-    >>> merge_sort([0, 5, 3, 2, 2])
-    [0, 2, 2, 3, 5]
-    >>> merge_sort([])
-    []
-    >>> merge_sort([-2, -5, -45])
-    [-45, -5, -2]
+    Example:
+        >>> merge_insertion_sort([8, 3, 5, 6])
+        [3, 5, 6, 8]
     """
+    if len(arr) <= 1:
+        return arr
 
-    def merge(left: list[int], right: list[int]) -> list[int]:
-        """
-        Merge two sorted lists into a single sorted list.
-
-        :param left: Left collection
-        :param right: Right collection
-        :return: Merged result
-        """
-        result = []
-        while left and right:
-            result.append(left.pop(0) if left[0] <= right[0] else right.pop(0))
-        result.extend(left)
-        result.extend(right)
-        return result
+    mid = len(arr) // 2
+    left = arr[:mid]
+    right = arr[mid:]
 
-    if len(collection) <= 1:
-        return collection
-    mid_index = len(collection) // 2
-    return merge(merge_sort(collection[:mid_index]), merge_sort(collection[mid_index:]))
+    left = merge_insertion_sort(left)
+    right = merge_insertion_sort(right)
 
+    return merge(left, right)
 
 if __name__ == "__main__":
-    if not hasattr(sys, "gettrace") or sys.gettrace() is None:
-        doctest.testmod()  # Only run tests if not debugging
-
-    try:
-        user_input = input("Enter numbers separated by a comma:\n").strip()
-        unsorted = [int(item) for item in user_input.split(",")]
-
-        sorted_list_merge_sort = merge_sort(unsorted)
-        sorted_list_iter_merge_sort = iter_merge_sort(
-            unsorted.copy()
-        )  # Use copy to avoid sorting the same list twice
-        sorted_list_merge_insertion_sort = merge_insertion_sort(unsorted.copy())
-
-        print(f"Unsorted list: {unsorted}")
-        print(f"Sorted list using merge_sort: {sorted_list_merge_sort}")
-        print(f"Sorted list using iter_merge_sort: {sorted_list_iter_merge_sort}")
-        print(
-            f"Sorted list using merge_insertion_sort: {sorted_list_merge_insertion_sort}"
-        )
-
-        print("Merge Sort Result:", *sorted_list_merge_sort, sep=",")
-        print("Iterative Merge Sort Result:", *sorted_list_iter_merge_sort, sep=",")
-        print(
-            "Merge Insertion Sort Result:", *sorted_list_merge_insertion_sort, sep=","
-        )
-    except ValueError:
-        print("Invalid input. Please enter valid integers separated by commas.")
+    import doctest
+    doctest.testmod()