Code review: fix 5 oldest code files with type hints and improvements

digital_image_processing/change_brightness.py

@@ -1,26 +1,54 @@
+"""
+Module for adjusting the brightness of images using PIL.
+"""
+
 from PIL import Image
 
 
-def change_brightness(img: Image, level: float) -> Image:
-    """
-    Change the brightness of a PIL Image to a given level.
-    """
+def change_brightness(img: Image.Image, level: float) -> Image.Image:
+    """Change the brightness of a PIL Image by the given level.
 
-    def brightness(c: int) -> float:
-        """
-        Fundamental Transformation/Operation that'll be performed on
-        every bit.
-        """
-        return 128 + level + (c - 128)
+    Args:
+        img: The input PIL Image to modify.
+        level: Brightness adjustment level between -255.0 (darker) and
+               255.0 (brighter). 0 means no change.
 
+    Returns:
+        A new Image with adjusted brightness.
+
+    Raises:
+        ValueError: If level is outside the valid range [-255.0, 255.0].
+
+    Examples:
+    >>> from PIL import Image
+    >>> img = Image.new("RGB", (10, 10), (128, 128, 128))
+    >>> bright_img = change_brightness(img, 50)
+    >>> bright_img.getpixel((5, 5))  # doctest: +ELLIPSIS
+    (178, 178, 178)
+    """
     if not -255.0 <= level <= 255.0:
         raise ValueError("level must be between -255.0 (black) and 255.0 (white)")
-    return img.point(brightness)
+
+    def adjust_pixel(c: int) -> int:
+        """Adjust a single pixel channel value by the brightness level."""
+        return max(0, min(255, c + int(level)))
+
+    return img.point(adjust_pixel)
 
 
 if __name__ == "__main__":
-    # Load image
-    with Image.open("image_data/lena.jpg") as img:
-        # Change brightness to 100
-        brigt_img = change_brightness(img, 100)
-        brigt_img.save("image_data/lena_brightness.png", format="png")
+    import sys
+
+    if len(sys.argv) != 4:
+        print("Usage: python change_brightness.py <input_image> <output_image> <level>")
+        print("  level: brightness adjustment from -255 to 255")
+        sys.exit(1)
+
+    input_path = sys.argv[1]
+    output_path = sys.argv[2]
+    level = float(sys.argv[3])
+
+    with Image.open(input_path) as img:
+        bright_img = change_brightness(img, level)
+        bright_img.save(output_path, format="png")
+    print(f"Brightness changed by {level} and saved to {output_path}")

dynamic_programming/abbreviation.py

@@ -1,35 +1,69 @@
 """
-https://www.hackerrank.com/challenges/abbr/problem
-You can perform the following operation on some string, :
+String abbreviation problem solved using dynamic programming.
 
-1. Capitalize zero or more of 's lowercase letters at some index i
-   (i.e., make them uppercase).
-2. Delete all of the remaining lowercase letters in .
+Given two strings 'a' and 'b', determine if 'a' can be transformed to 'b' by:
+1. Capitalizing zero or more of 'a's lowercase letters at any index.
+2. Deleting all remaining lowercase letters.
+
+Reference: https://www.hackerrank.com/challenges/Abbr/problem
 
 Example:
-a=daBcd and b="ABC"
-daBcd -> capitalize a and c(dABCd) -> remove d (ABC)
+    a = "daBcd" and b = "ABC"
+    "daBcd" -> capitalize 'a' and 'c' to get "dABCd" -> delete 'd' to get "ABC"
 """
 
 
-def abbr(a: str, b: str) -> bool:
-    """
-    >>> abbr("daBcd", "ABC")
+def abbreviation(a: str, b: str) -> bool:
+    """Check if string 'a' can be transformed to 'b'.
+
+    Uses dynamic programming where dp[i][j] indicates whether the first i
+    characters of 'a' can be transformed to the first j characters of 'b'.
+
+    Args:
+        a: The source string containing lowercase and uppercase letters.
+        b: The target string containing only uppercase letters.
+
+    Returns:
+        True if 'a' can be transformed to 'b', False otherwise.
+
+    Examples:
+    >>> abbreviation("daBcd", "ABC")
+    True
+    >>> abbreviation("dBcd", "ABC")
+    False
+    >>> abbreviation("ABC", "ABC")
     True
-    >>> abbr("dBcd", "ABC")
+    >>> abbreviation("abc", "ABC")
     False
+    >>> abbreviation("abCD", "ABCD")
+    True
     """
     n = len(a)
     m = len(b)
-    dp = [[False for _ in range(m + 1)] for _ in range(n + 1)]
+
+    # Early exit: if 'b' has lowercase letters, it can never match
+    if b != b.upper():
+        return False
+
+    # Early exit: if 'a' has more uppercase letters than the length of 'b'
+    a_upper_count = sum(1 for c in a if c.isupper())
+    if a_upper_count > m:
+        return False
+
+    dp = [[False] * (m + 1) for _ in range(n + 1)]
     dp[0][0] = True
+
     for i in range(n):
         for j in range(m + 1):
-            if dp[i][j]:
-                if j < m and a[i].upper() == b[j]:
-                    dp[i + 1][j + 1] = True
-                if a[i].islower():
-                    dp[i + 1][j] = True
+            if not dp[i][j]:
+                continue
+
+            if j < m and a[i].upper() == b[j]:
+                dp[i + 1][j + 1] = True
+
+            if a[i].islower():
+                dp[i + 1][j] = True
+
     return dp[n][m]
 
 

graphs/g_topological_sort.py

@@ -1,47 +1,131 @@
-# Author: Phyllipe Bezerra (https://github.com/pmba)
+"""
+Graph topological sort implementation using Depth-First Search (DFS).
 
-clothes = {
-    0: "underwear",
-    1: "pants",
-    2: "belt",
-    3: "suit",
-    4: "shoe",
-    5: "socks",
-    6: "shirt",
-    7: "tie",
-    8: "watch",
-}
+A topological sort or topological ordering of a directed graph is a linear
+ordering of its vertices in which each vertex comes before all vertices
+to which it has outgoing edges.
 
-graph = [[1, 4], [2, 4], [3], [], [], [4], [2, 7], [3], []]
+For example, the graph representing clothing dependencies:
+- underwear -> pants -> belt -> suit
+- shirt -> tie -> suit
+- socks -> shoes
 
-visited = [0 for x in range(len(graph))]
-stack = []
+Author: Phyllipe Bezerra (https://github.com/pmba)
+"""
 
+from collections.abc import Sequence
 
-def print_stack(stack, clothes):
-    order = 1
-    while stack:
-        current_clothing = stack.pop()
-        print(order, clothes[current_clothing])
-        order += 1
 
+class TopologicalSort:
+    """Topological sort implementation using DFS."""
 
-def depth_first_search(u, visited, graph):
-    visited[u] = 1
-    for v in graph[u]:
-        if not visited[v]:
-            depth_first_search(v, visited, graph)
+    def __init__(
+        self, graph: list[list[int]], labels: dict[int, str] | None = None
+    ) -> None:
+        """Initialize the topological sorter.
+
+        Args:
+            graph: Adjacency list representation where graph[u] contains
+                   all vertices v such that there is an edge from u to v.
+            labels: Optional mapping from vertex indices to label strings
+                    for pretty printing results.
+        """
+        self.graph = graph
+        self.labels = labels or {}
+        self.n = len(graph)
+        self.visited: list[int] = [0] * self.n
+        self.stack: list[int] = []
+
+    def _depth_first_search(self, u: int) -> None:
+        """Perform DFS from vertex u, adding to stack after exploring all neighbors."""
+        self.visited[u] = 1
+        for v in self.graph[u]:
+            if not self.visited[v]:
+                self._depth_first_search(v)
+        self.stack.append(u)
+
+    def sort(self) -> list[int]:
+        """Compute and return the topological ordering of vertices.
+
+        Returns:
+            A list of vertices in topological order (each vertex appears before
+            all vertices reachable from it).
+        """
+        self.stack = []
+        self.visited = [0] * self.n
+
+        for v in range(self.n):
+            if not self.visited[v]:
+                self._depth_first_search(v)
+
+        return self.stack[::-1]
+
+    def print_sorted(self, order: list[int]) -> None:
+        """Print the vertices in topological order with their labels.
+
+        Args:
+            order: A list of vertices in topological order.
+        """
+        for i, vertex in enumerate(order, 1):
+            label = self.labels.get(vertex, str(vertex))
+            print(f"{i}. {label}")
 
-    stack.append(u)
 
+def topological_sort(graph: list[list[int]], visited: list[int]) -> list[int]:
+    """Topological sort of a directed acyclic graph using DFS.
+
+    Args:
+        graph: Adjacency list representation of the graph.
+        visited: List to track visited vertices (modified in place).
+
+    Returns:
+        Vertices in topological order.
+
+    Examples:
+    >>> graph = [[1, 2], [3], [3], []]
+    >>> visited = [0] * len(graph)
+    >>> topological_sort(graph, visited)
+    [0, 2, 1, 3]
+    """
+    stack = []
+
+    def dfs(u: int) -> None:
+        visited[u] = 1
+        for v in graph[u]:
+            if not visited[v]:
+                dfs(v)
+        stack.append(u)
 
-def topological_sort(graph, visited):
     for v in range(len(graph)):
         if not visited[v]:
-            depth_first_search(v, visited, graph)
+            dfs(v)
+
+    return stack[::-1]
 
 
 if __name__ == "__main__":
-    topological_sort(graph, visited)
-    print(stack)
-    print_stack(stack, clothes)
+    # Example: Clothing dependencies
+    clothes = {
+        0: "underwear",
+        1: "pants",
+        2: "belt",
+        3: "suit",
+        4: "shoe",
+        5: "socks",
+        6: "shirt",
+        7: "tie",
+        8: "watch",
+    }
+
+    graph = [[1, 4], [2, 4], [3], [], [], [4], [2, 7], [3], []]
+
+    # Using the class-based interface
+    sorter = TopologicalSort(graph, clothes)
+    order = sorter.sort()
+    sorter.print_sorted(order)
+
+    # Also demonstrate the functional interface
+    print("\n--- Using functional interface ---")
+    visited = [0] * len(graph)
+    result = topological_sort(graph, visited)
+    print(result)

searches/sentinel_linear_search.py

@@ -1,5 +1,8 @@
 """
-This is pure Python implementation of sentinel linear search algorithm
+This is pure Python implementation of sentinel linear search algorithm.
+
+The sentinel linear search improves on linear search by adding a sentinel
+(target value) at the end of the list to avoid bounds checking on each iteration.
 
 For doctests run following command:
 python -m doctest -v sentinel_linear_search.py
@@ -10,26 +13,30 @@
 python sentinel_linear_search.py
 """
 
+from collections.abc import Sequence
+from typing import Any
+
 
-def sentinel_linear_search(sequence, target):
-    """Pure implementation of sentinel linear search algorithm in Python
+def sentinel_linear_search(sequence: list, target: Any) -> int | None:
+    """Pure implementation of sentinel linear search algorithm in Python.
 
-    :param sequence: some sequence with comparable items
-    :param target: item value to search
-    :return: index of found item or None if item is not found
+    Args:
+        sequence: A list of comparable items. Note: this list will be modified
+                  temporarily by appending the target value (restored before return).
+        target: The item value to search for.
+
+    Returns:
+        The index of the found item, or None if the item is not found.
 
     Examples:
     >>> sentinel_linear_search([0, 5, 7, 10, 15], 0)
     0
-
     >>> sentinel_linear_search([0, 5, 7, 10, 15], 15)
     4
-
     >>> sentinel_linear_search([0, 5, 7, 10, 15], 5)
     1
-
-    >>> sentinel_linear_search([0, 5, 7, 10, 15], 6)
-
+    >>> sentinel_linear_search([0, 5, 7, 10, 15], 6) is None
+    True
     """
     sequence.append(target)
 
@@ -39,7 +46,7 @@
 
     sequence.pop()
 
-    if index == len(sequence):
+    if index >= len(sequence):
         return None
 
     return index
@@ -53,6 +60,6 @@
     target = int(target_input)
     result = sentinel_linear_search(sequence, target)
     if result is not None:
-        print(f"{target} found at positions: {result}")
+        print(f"{target} found at position: {result}")
     else:
         print("Not found")