Happy number (new algorithm)

maths/special_numbers/happy_number.py

@@ -0,0 +1,48 @@
+def is_happy_number(number: int) -> bool:
+ """
+ A happy number is a number which eventually reaches 1 when replaced by the sum of
+ the square of each digit.
+
+ :param number: The number to check for happiness.
+ :return: True if the number is a happy number, False otherwise.
+
+ >>> is_happy_number(19)
+ True
+ >>> is_happy_number(2)
+ False
+ >>> is_happy_number(23)
+ True
+ >>> is_happy_number(1)
+ True
+ >>> is_happy_number(0)
+ Traceback (most recent call last):
+ ...
+ ValueError: number=0 must be a positive integer
+ >>> is_happy_number(-19)
+ Traceback (most recent call last):
+ ...
+ ValueError: number=-19 must be a positive integer
+ >>> is_happy_number(19.1)
+ Traceback (most recent call last):
+ ...
+ ValueError: number=19.1 must be a positive integer
+ >>> is_happy_number("happy")
+ Traceback (most recent call last):
+ ...
+ ValueError: number='happy' must be a positive integer
+ """
+ if not isinstance(number, int) or number <= 0:
+ msg = f"{number=} must be a positive integer"
+ raise ValueError(msg)
+
+ seen = set()
+ while number != 1 and number not in seen:
+ seen.add(number)
+ number = sum(int(digit) ** 2 for digit in str(number))
+ return number == 1
+
+
+if __name__ == "__main__":
+ import doctest
+
+ doctest.testmod()