From ddd4efd7689494f52f837064f5abb76186a41bdd Mon Sep 17 00:00:00 2001
From: Nefelibata <124799179+MeiSiristhebest@users.noreply.github.com>
Date: Sat, 1 Aug 2026 13:46:47 +0800
Subject: [PATCH 1/2] Add digital root algorithm

---
 maths/digital_root.py | 46 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 maths/digital_root.py

diff --git a/maths/digital_root.py b/maths/digital_root.py
new file mode 100644
index 000000000000..ac529e53b940
--- /dev/null
+++ b/maths/digital_root.py
@@ -0,0 +1,46 @@
+from __future__ import annotations
+
+"""
+Digital Root.
+The digital root (also known as the repeated digital sum) of a non-negative
+integer is the (single digit) value obtained by an iterative process of summing
+digits: on each iteration the digits of the previous result are summed, and the
+process continues until a single-digit number is reached.
+
+For more information see:
+https://en.wikipedia.org/wiki/Digital_root
+"""
+
+
+def digital_root(n: int) -> int:
+    """
+    Return the digital root of a non-negative integer n.
+
+    The digital root is the single-digit value obtained by repeatedly summing
+    the decimal digits of n until only one digit remains. The input is taken by
+    its absolute value, so negative numbers behave like their positive
+    counterpart.
+
+    >>> digital_root(0)
+    0
+    >>> digital_root(9)
+    9
+    >>> digital_root(38)
+    2
+    >>> digital_root(12345)
+    6
+    >>> digital_root(-45)
+    9
+    >>> digital_root(999999999999)
+    9
+    """
+    n = abs(n)
+    while n >= 10:
+        n = sum(int(digit) for digit in str(n))
+    return n
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()

From 7f85add0a977446573b363d552b0e8ca863ee7b8 Mon Sep 17 00:00:00 2001
From: Nefelibata <124799179+MeiSiristhebest@users.noreply.github.com>
Date: Sat, 1 Aug 2026 14:50:53 +0800
Subject: [PATCH 2/2] refactor: use descriptive parameter name `number` instead
 of `n` (algorithms-keeper)

---
 maths/digital_root.py | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/maths/digital_root.py b/maths/digital_root.py
index ac529e53b940..bb809c98bd35 100644
--- a/maths/digital_root.py
+++ b/maths/digital_root.py
@@ -12,12 +12,12 @@
 """
 
 
-def digital_root(n: int) -> int:
+def digital_root(number: int) -> int:
     """
-    Return the digital root of a non-negative integer n.
+    Return the digital root of a non-negative integer number.
 
     The digital root is the single-digit value obtained by repeatedly summing
-    the decimal digits of n until only one digit remains. The input is taken by
+    the decimal digits of number until only one digit remains. The input is taken by
     its absolute value, so negative numbers behave like their positive
     counterpart.
 
@@ -34,10 +34,10 @@ def digital_root(n: int) -> int:
     >>> digital_root(999999999999)
     9
     """
-    n = abs(n)
-    while n >= 10:
-        n = sum(int(digit) for digit in str(n))
-    return n
+    number = abs(number)
+    while number >= 10:
+        number = sum(int(digit) for digit in str(number))
+    return number
 
 
 if __name__ == "__main__":