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https://github.com/TheAlgorithms/Ruby
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35 lines
572 B
Ruby
35 lines
572 B
Ruby
# Challenge name: Add Digits
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#
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# Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.
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#
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# Example:
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#
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# Input: 38
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# Output: 2
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# Explanation: 3 + 8 = 11, 1 + 1 = 2.
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#
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# Approach: Mathematical: Digital Root
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#
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# https://en.wikipedia.org/wiki/Digital_root
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# https://brilliant.org/wiki/digital-root/
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#
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#
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# Complexity Analysis
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#
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# Time Complexity: O(1).
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# Space Complexity: O(1).
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def add_digits(num)
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return 0 if num == 0
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return 9 if num % 9 == 0
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num % 9
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end
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puts(add_digits(38))
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# # => 2
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puts(add_digits(284))
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# # => 5
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