Question

How to count the number of digits in an integer with Ruby

Answer 1

def count_digits_string(value)
  # Convert the number to a string
  text = value.to_s

  # If negative, ignore the leading '-'
  if text.start_with?("-")
    return text.length - 1
  end

  text.length
end

number = -12345
digits = count_digits_string(number)

puts "Number: #{number}"
puts "Digit count (String method): #{digits}"


=begin
run:

Number: -12345
Digit count (String method): 5

=end

 

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Answer 2

def count_digits_log10(value)
  num = value.abs

  # Zero must be handled explicitly
  return 1 if num == 0

  # Use floor(log10(n)) + 1
  Math.log10(num).floor + 1
end

number = 987_654_321
digits = count_digits_log10(number)

puts "Number: #{number}"
puts "Digit count (log10 method): #{digits}"



=begin
run:

Number: 987654321
Digit count (log10 method): 9

=end

 

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