From 34294b564144d94530ff1be8b0f6e61465db3480 Mon Sep 17 00:00:00 2001
From: Du Yuanchao <shellhub.me@gmail.com>
Date: Mon, 17 Aug 2020 02:31:06 +0800
Subject: [PATCH] Update sum_of_digits.py (#2319)

* * support negative number
* add different version

* fixup! Format Python code with psf/black push

* sum(int(c) for c in str(abs(n)))

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>
---
 DIRECTORY.md           |   5 ++
 maths/sum_of_digits.py | 133 ++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 137 insertions(+), 1 deletion(-)

diff --git a/DIRECTORY.md b/DIRECTORY.md
index f97a8e55f..1530ed763 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -297,6 +297,7 @@
     * [Power Iteration](https://github.com/TheAlgorithms/Python/blob/master/linear_algebra/src/power_iteration.py)
     * [Rayleigh Quotient](https://github.com/TheAlgorithms/Python/blob/master/linear_algebra/src/rayleigh_quotient.py)
     * [Test Linear Algebra](https://github.com/TheAlgorithms/Python/blob/master/linear_algebra/src/test_linear_algebra.py)
+    * [Transformations 2D](https://github.com/TheAlgorithms/Python/blob/master/linear_algebra/src/transformations_2d.py)
 
 ## Machine Learning
   * [Astar](https://github.com/TheAlgorithms/Python/blob/master/machine_learning/astar.py)
@@ -580,6 +581,10 @@
     * [Sol32](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_32/sol32.py)
   * Problem 33
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_33/sol1.py)
+  * Problem 34
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_34/sol1.py)
+  * Problem 35
+    * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_35/sol1.py)
   * Problem 36
     * [Sol1](https://github.com/TheAlgorithms/Python/blob/master/project_euler/problem_36/sol1.py)
   * Problem 40
diff --git a/maths/sum_of_digits.py b/maths/sum_of_digits.py
index 88baf2ca2..64da00d46 100644
--- a/maths/sum_of_digits.py
+++ b/maths/sum_of_digits.py
@@ -1,3 +1,6 @@
+from timeit import timeit
+
+
 def sum_of_digits(n: int) -> int:
     """
     Find the sum of digits of a number.
@@ -6,7 +9,12 @@ def sum_of_digits(n: int) -> int:
     15
     >>> sum_of_digits(123)
     6
+    >>> sum_of_digits(-123)
+    6
+    >>> sum_of_digits(0)
+    0
     """
+    n = -n if n < 0 else n
     res = 0
     while n > 0:
         res += n % 10
@@ -14,5 +22,128 @@ def sum_of_digits(n: int) -> int:
     return res
 
 
+def sum_of_digits_recursion(n: int) -> int:
+    """
+    Find the sum of digits of a number using recursion
+
+    >>> sum_of_digits_recursion(12345)
+    15
+    >>> sum_of_digits_recursion(123)
+    6
+    >>> sum_of_digits_recursion(-123)
+    6
+    >>> sum_of_digits_recursion(0)
+    0
+    """
+    n = -n if n < 0 else n
+    return n if n < 10 else n % 10 + sum_of_digits(n // 10)
+
+
+def sum_of_digits_compact(n: int) -> int:
+    """
+    Find the sum of digits of a number
+
+    >>> sum_of_digits_compact(12345)
+    15
+    >>> sum_of_digits_compact(123)
+    6
+    >>> sum_of_digits_compact(-123)
+    6
+    >>> sum_of_digits_compact(0)
+    0
+    """
+    return sum(int(c) for c in str(abs(n)))
+
+
+def benchmark() -> None:
+    """
+    Benchmark code for comparing 3 functions,
+    with 3 different length int values.
+    """
+    print("\nFor small_num = ", small_num, ":")
+    print(
+        "> sum_of_digits()",
+        "\t\tans =",
+        sum_of_digits(small_num),
+        "\ttime =",
+        timeit("z.sum_of_digits(z.small_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+    print(
+        "> sum_of_digits_recursion()",
+        "\tans =",
+        sum_of_digits_recursion(small_num),
+        "\ttime =",
+        timeit("z.sum_of_digits_recursion(z.small_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+    print(
+        "> sum_of_digits_compact()",
+        "\tans =",
+        sum_of_digits_compact(small_num),
+        "\ttime =",
+        timeit("z.sum_of_digits_compact(z.small_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+
+    print("\nFor medium_num = ", medium_num, ":")
+    print(
+        "> sum_of_digits()",
+        "\t\tans =",
+        sum_of_digits(medium_num),
+        "\ttime =",
+        timeit("z.sum_of_digits(z.medium_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+    print(
+        "> sum_of_digits_recursion()",
+        "\tans =",
+        sum_of_digits_recursion(medium_num),
+        "\ttime =",
+        timeit("z.sum_of_digits_recursion(z.medium_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+    print(
+        "> sum_of_digits_compact()",
+        "\tans =",
+        sum_of_digits_compact(medium_num),
+        "\ttime =",
+        timeit("z.sum_of_digits_compact(z.medium_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+
+    print("\nFor large_num = ", large_num, ":")
+    print(
+        "> sum_of_digits()",
+        "\t\tans =",
+        sum_of_digits(large_num),
+        "\ttime =",
+        timeit("z.sum_of_digits(z.large_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+    print(
+        "> sum_of_digits_recursion()",
+        "\tans =",
+        sum_of_digits_recursion(large_num),
+        "\ttime =",
+        timeit("z.sum_of_digits_recursion(z.large_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+    print(
+        "> sum_of_digits_compact()",
+        "\tans =",
+        sum_of_digits_compact(large_num),
+        "\ttime =",
+        timeit("z.sum_of_digits_compact(z.large_num)", setup="import __main__ as z"),
+        "seconds",
+    )
+
+
 if __name__ == "__main__":
-    print(sum_of_digits(12345))  # ===> 15
+    small_num = 262144
+    medium_num = 1125899906842624
+    large_num = 1267650600228229401496703205376
+    benchmark()
+    import doctest
+
+    doctest.testmod()