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Nefelibata
be65e47b54
* Add digital root algorithm * refactor: use descriptive parameter name `number` instead of `n` (algorithms-keeper) Also see: project_euler/problem_092/sol1.py
47 lines
1.2 KiB
Python
47 lines
1.2 KiB
Python
from __future__ import annotations
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"""
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Digital Root.
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The digital root (also known as the repeated digital sum) of a non-negative
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integer is the (single digit) value obtained by an iterative process of summing
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digits: on each iteration the digits of the previous result are summed, and the
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process continues until a single-digit number is reached.
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For more information see:
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https://en.wikipedia.org/wiki/Digital_root
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"""
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def digital_root(number: int) -> int:
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"""
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Return the digital root of a non-negative integer number.
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The digital root is the single-digit value obtained by repeatedly summing
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the decimal digits of number until only one digit remains. The input is taken by
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its absolute value, so negative numbers behave like their positive
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counterpart.
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>>> digital_root(0)
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0
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>>> digital_root(9)
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9
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>>> digital_root(38)
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2
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>>> digital_root(12345)
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6
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>>> digital_root(-45)
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9
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>>> digital_root(999999999999)
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9
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"""
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number = abs(number)
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while number >= 10:
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number = sum(int(digit) for digit in str(number))
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return number
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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