refactor(searches): add type annotations, docstring, and doctests to double_linear_search_recursion.py

Author: vav7

searches/double_linear_search.py

@@ -1,37 +1,51 @@
-from __future__ import annotations
+"""
+Recursive Double Linear Search Algorithm
 
+Searches for a target element in a list by recursively checking both ends simultaneously.
+"""
 
-def double_linear_search(array: list[int], search_item: int) -> int:
+
+def double_linear_search_recursion(
+    sequence: list[int], target: int, start: int = 0, end: int | None = None
+) -> int:
     """
-    Iterate through the array from both sides to find the index of search_item.
+    Recursively searches for target in sequence from both ends.
+
+    Time Complexity: O(n)
+    Space Complexity: O(n) due to recursive call stack
 
-    :param array: the array to be searched
-    :param search_item: the item to be searched
-    :return the index of search_item, if search_item is in array, else -1
+    :param sequence: A list of integers.
+    :param target: The integer value to search for.
+    :param start: Starting index for search window.
+    :param end: Ending index for search window.
+    :return: Index of target if found, else -1.
 
-    Examples:
-    >>> double_linear_search([1, 5, 5, 10], 1)
+    >>> double_linear_search_recursion([1, 2, 3, 4, 5], 1)
     0
-    >>> double_linear_search([1, 5, 5, 10], 5)
-    1
-    >>> double_linear_search([1, 5, 5, 10], 100)
+    >>> double_linear_search_recursion([1, 2, 3, 4, 5], 5)
+    4
+    >>> double_linear_search_recursion([1, 2, 3, 4, 5], 3)
+    2
+    >>> double_linear_search_recursion([1, 2, 3, 4, 5], 6)
+    -1
+    >>> double_linear_search_recursion([], 3)
     -1
-    >>> double_linear_search([1, 5, 5, 10], 10)
-    3
     """
-    # define the start and end index of the given array
-    start_ind, end_ind = 0, len(array) - 1
-    while start_ind <= end_ind:
-        if array[start_ind] == search_item:
-            return start_ind
-        elif array[end_ind] == search_item:
-            return end_ind
-        else:
-            start_ind += 1
-            end_ind -= 1
-    # returns -1 if search_item is not found in array
-    return -1
+    if end is None:
+        end = len(sequence) - 1
+
+    if start > end:
+        return -1
+
+    if sequence[start] == target:
+        return start
+    if sequence[end] == target:
+        return end
+
+    return double_linear_search_recursion(sequence, target, start + 1, end - 1)
 
 
 if __name__ == "__main__":
-    print(double_linear_search(list(range(100)), 40))
+    import doctest
+
+    doctest.testmod()