Add Krishnamurty Number to Math algorithms (keon#728)

Nanak360 · Nanak Bandyopadhyay · web-flow · commit 30512d9b181f · 2020-10-22T21:48:08.000-05:00
* add Krishnamurthy Number to Math algorithms

* tests added for krishnamurthy number, readme update

* Update function name of krishnamurthy_number.py

Co-authored-by: Nanak Bandyopadhyay &lt;nanakbandyopadhay@hotmail.com&gt;
diff --git a/README.md b/README.md
@@ -209,6 +209,7 @@ If you want to uninstall algorithms, it is as simple as:
     - [gcd/lcm](algorithms/maths/gcd.py)
     - [generate_strobogrammtic](algorithms/maths/generate_strobogrammtic.py)
     - [is_strobogrammatic](algorithms/maths/is_strobogrammatic.py)
+    - [krishnamurthy_number](algorithms/maths/krishnamurthy_number.py)
     - [modular_exponential](algorithms/maths/modular_exponential.py)
     - [modular_inverse](algorithms/maths/modular_inverse.py)
     - [next_bigger](algorithms/maths/next_bigger.py)
diff --git a/algorithms/maths/__init__.py b/algorithms/maths/__init__.py
@@ -19,3 +19,4 @@
 from .find_primitive_root_simple import *
 from .diffie_hellman_key_exchange import *
 from .power import *
+from .krishnamurthy_number import *
diff --git a/algorithms/maths/krishnamurthy_number.py b/algorithms/maths/krishnamurthy_number.py
@@ -0,0 +1,43 @@
+"""
+A Krishnamurthy number is a number whose sum total of the factorials of each digit is equal to the number itself.
+
+Here's what I mean by that:
+
+"145" is a Krishnamurthy Number because,
+1! + 4! + 5! = 1 + 24 + 120 = 145
+
+"40585" is also a Krishnamurthy Number.
+4! + 0! + 5! + 8! + 5! = 40585
+
+"357" or "25965" is NOT a Krishnamurthy Number
+3! + 5! + 7! = 6 + 120 + 5040 != 357
+
+The following function will check if a number is a Krishnamurthy Number or not and return a boolean value.
+"""
+
+
+def find_factorial(n):
+    fact = 1
+    while n != 0:
+        fact *= n
+        n -= 1
+    return fact
+
+
+def krishnamurthy_number(n):
+    if n == 0:
+        return False
+    sum_of_digits = 0   # will hold sum of FACTORIAL of digits
+    temp = n
+
+    while temp != 0:
+
+        # get the factorial of of the last digit of n and add it to sum_of_digits
+        sum_of_digits += find_factorial(temp % 10)
+
+        # replace value of temp by temp/10
+        # i.e. will remove the last digit from temp
+        temp //= 10
+
+    # returns True if number is krishnamurthy
+    return (sum_of_digits == n)
diff --git a/tests/test_maths.py b/tests/test_maths.py
@@ -21,7 +21,8 @@
     cosine_similarity,
     find_order,
     find_primitive_root,
-    alice_private_key, alice_public_key, bob_private_key, bob_public_key, alice_shared_key, bob_shared_key, diffie_hellman_key_exchange
+    alice_private_key, alice_public_key, bob_private_key, bob_public_key, alice_shared_key, bob_shared_key, diffie_hellman_key_exchange,
+    krishnamurthy_number,
 )
 
 import unittest
@@ -393,6 +394,21 @@ def test_find_order_simple(self):
         self.assertEqual(-1, find_order(128, 256))
         self.assertEqual(352, find_order(3, 353))
 
+class TestKrishnamurthyNumber(unittest.TestCase):
+    """[summary]
+    Test for the file krishnamurthy_number.py
+
+    Arguments:
+        unittest {[type]} -- [description]
+    """
+    
+    def test_krishnamurthy_number(self):
+        self.assertFalse(krishnamurthy_number(0))
+        self.assertTrue(krishnamurthy_number(2))
+        self.assertTrue(krishnamurthy_number(1))
+        self.assertTrue(krishnamurthy_number(145))
+        self.assertTrue(krishnamurthy_number(40585))
+
 
 class TestDiffieHellmanKeyExchange(unittest.TestCase):
     """[summary]
