From 5130f3a6c01c595f1a542a984f8235a06451429a Mon Sep 17 00:00:00 2001
From: Toshaksha <147024929+Toshaksha@users.noreply.github.com>
Date: Mon, 7 Jul 2025 14:43:25 +0530
Subject: [PATCH 1/3] Add simple recursion examples: factorial, fibonacci,
 sum_of_digits

---
 other/simple_recursion.py | 100 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)
 create mode 100644 other/simple_recursion.py

diff --git a/other/simple_recursion.py b/other/simple_recursion.py
new file mode 100644
index 000000000000..0af35816859f
--- /dev/null
+++ b/other/simple_recursion.py
@@ -0,0 +1,100 @@
+"""
+Simple Recursion Examples.
+
+This module contains a few basic examples of recursion for beginners.
+
+Functions:
+- factorial(n): Calculate factorial of n.
+- fibonacci(n): Calculate nth Fibonacci number.
+- sum_of_digits(n): Calculate sum of digits of n.
+
+Each function has doctests to verify correct behavior.
+"""
+
+def factorial(n: int) -> int:
+    """
+    Calculate the factorial of a non-negative integer n using recursion.
+
+    Args:
+        n (int): Non-negative integer.
+
+    Returns:
+        int: Factorial of n.
+
+    Raises:
+        ValueError: If n is negative.
+
+    Examples:
+    >>> factorial(5)
+    120
+    >>> factorial(0)
+    1
+    >>> factorial(1)
+    1
+    """
+    if n < 0:
+        raise ValueError("Input must be a non-negative integer")
+    if n == 0:
+        return 1
+    return n * factorial(n - 1)
+
+
+def fibonacci(n: int) -> int:
+    """
+    Calculate the nth Fibonacci number using recursion.
+
+    Args:
+        n (int): Non-negative integer index.
+
+    Returns:
+        int: nth Fibonacci number.
+
+    Raises:
+        ValueError: If n is negative.
+
+    Examples:
+    >>> fibonacci(0)
+    0
+    >>> fibonacci(1)
+    1
+    >>> fibonacci(7)
+    13
+    """
+    if n < 0:
+        raise ValueError("Input must be a non-negative integer")
+    if n <= 1:
+        return n
+    return fibonacci(n - 1) + fibonacci(n - 2)
+
+
+def sum_of_digits(n: int) -> int:
+    """
+    Calculate the sum of digits of a non-negative integer n using recursion.
+
+    Args:
+        n (int): Non-negative integer.
+
+    Returns:
+        int: Sum of digits of n.
+
+    Raises:
+        ValueError: If n is negative.
+
+    Examples:
+    >>> sum_of_digits(123)
+    6
+    >>> sum_of_digits(0)
+    0
+    >>> sum_of_digits(999)
+    27
+    """
+    if n < 0:
+        raise ValueError("Input must be a non-negative integer")
+    if n == 0:
+        return 0
+    return n % 10 + sum_of_digits(n // 10)
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()

From d08a47d3c9ec8e662705308ac40657041ac88f86 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 7 Jul 2025 09:24:34 +0000
Subject: [PATCH 2/3] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 other/simple_recursion.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/other/simple_recursion.py b/other/simple_recursion.py
index 0af35816859f..7f964dcfe041 100644
--- a/other/simple_recursion.py
+++ b/other/simple_recursion.py
@@ -11,6 +11,7 @@
 Each function has doctests to verify correct behavior.
 """
 
+
 def factorial(n: int) -> int:
     """
     Calculate the factorial of a non-negative integer n using recursion.
@@ -97,4 +98,5 @@ def sum_of_digits(n: int) -> int:
 
 if __name__ == "__main__":
     import doctest
+
     doctest.testmod()

From 40b8b82d0c48607e47eeecd8fa87d060bca07708 Mon Sep 17 00:00:00 2001
From: Toshaksha <Toshaksha@users.noreply.github.com>
Date: Sat, 12 Jul 2025 05:05:23 +0000
Subject: [PATCH 3/3] updating DIRECTORY.md

---
 DIRECTORY.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/DIRECTORY.md b/DIRECTORY.md
index 81d6f4c70864..dd9588a1eeb8 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -875,6 +875,7 @@
   * [Quine](other/quine.py)
   * [Scoring Algorithm](other/scoring_algorithm.py)
   * [Sdes](other/sdes.py)
+  * [Simple Recursion](other/simple_recursion.py)
   * [Tower Of Hanoi](other/tower_of_hanoi.py)
   * [Word Search](other/word_search.py)