Finished writing solution and test files for sort colors,ready for co…

…de review

solutions/sort_colors.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+A module for sorting a list of numbers based on their colors.
+
+Module contents:
+    - sort_colors: sorts a list of integers representing colors (0, 1, 2) in ascending order.
+
+Dependencies:
+    - typing: Used for type annotations (List).
+
+Notes:
+    - Does not use built-in sorting functions or libraries such as `sorted()` or `sort()`.
+    - Implements an in-place counting sort approach.
+    - Time complexity: O(n)
+    - Space complexity: O(1) (in-place).
+
+Created on 26 12 2024
+@author: Mohamed Elnageeb
+"""
+
+from typing import List  # Importing List for type annotations
+
+
+def sort_colors(nums: List[int]) -> None:
+    """
+    Sorts a given list of integers representing colors (0, 1, 2) in-place.
+
+    This function implements sorting logic manually using a counting sort approach and does not use
+    any built-in sorting functions or libraries, such as `sorted()` or `sort()`.
+
+    Time Complexity:
+        O(n): Iterates through the list once to count occurrences and again to modify it in-place.
+
+    Space Complexity:
+        O(1): Uses a fixed-size counter array of size 3. No additional space is used.
+
+    Parameters:
+        nums: List[int]
+            A list of integers where each integer is 0, 1, or 2. Modified in-place.
+
+    Returns:
+        None
+
+    Raises:
+        AssertionError: if the input is not a list or contains invalid elements.
+
+    Examples:
+    >>> nums = [0, 2, 1]
+    >>> sort_colors(nums)
+    >>> nums
+    [0, 1, 2]
+
+    >>> nums = [1]
+    >>> sort_colors(nums)
+    >>> nums
+    [1]
+
+    >>> nums = [2, 1, 1, 0, 2]
+    >>> sort_colors(nums)
+    >>> nums
+    [0, 1, 1, 2, 2]
+    """
+    # Validate input
+    assert isinstance(nums, list), "Input must be a list."
+    assert all(0 <= number <= 2 for number in nums), "All elements must be 0, 1, or 2."
+
+    # Create a counter array to store the count of each number
+    counter_array = [0] * 3
+
+    # Count occurrences of each number
+    for number in nums:
+        counter_array[number] += 1
+
+    # Rebuild the nums array in-place
+    index = 0
+    for number in range(3):
+        for _ in range(counter_array[number]):
+            nums[index] = number
+            index += 1

solutions/tests/test_sort_colors.py

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+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+"""
+Created on 26 10 2024
+
+@author: Mohamed Elnageeb
+"""
+
+import random
+import unittest
+
+# Import the function to be tested
+from ..sort_colors import sort_colors
+
+
+class TestSortColors(unittest.TestCase):
+    """Test the sort_colors function"""
+
+    def test_empty_list(self):
+        """It should handle an empty list"""
+        nums = []
+        sort_colors(nums)
+        self.assertEqual(nums, [])
+
+    def test_single_element(self):
+        """It should handle a list with one element"""
+        nums = [1]
+        sort_colors(nums)
+        self.assertEqual(nums, [1])
+
+    def test_all_same_elements(self):
+        """It should handle a list with all elements being the same"""
+        nums = [2, 2, 2]
+        sort_colors(nums)
+        self.assertEqual(nums, [2, 2, 2])
+
+    def test_already_sorted(self):
+        """It should not modify an already sorted list"""
+        nums = [0, 0, 1, 1, 2, 2]
+        sort_colors(nums)
+        self.assertEqual(nums, [0, 0, 1, 1, 2, 2])  # Fixed expected output
+
+    def test_unsorted_list(self):
+        """It should sort an unsorted list"""
+        nums = [2, 0, 2, 1, 1, 0]
+        sort_colors(nums)
+        self.assertEqual(nums, [0, 0, 1, 1, 2, 2])
+
+    def test_large_list(self):
+        """It should handle a large list"""
+        nums = [0, 2, 1] * 100000
+        sort_colors(nums)
+        self.assertEqual(nums, [0] * 100000 + [1] * 100000 + [2] * 100000)
+
+    def test_not_a_list(self):
+        """It should raise an assertion error if the input is not a list"""
+        with self.assertRaises(AssertionError):
+            sort_colors("not a list")
+
+    def test_invalid_elements(self):
+        """It should raise an assertion error for invalid elements"""
+        nums = [0, 1, 3]  # Invalid element 3
+        with self.assertRaises(AssertionError):
+            sort_colors(nums)
+
+    def test_randomly_generated_list(self):
+        """It should sort an unsorted list"""
+        nums = [random.randint(0, 2) for i in range(1000)]
+        expected = list(sorted(nums))
+        sort_colors(nums)
+        self.assertEqual(nums, expected)