Integer to roman numeral

Isabelle Viktoria Maciohsek · Python, Math, String · Nov 2, 2020

Converts an integer to its roman numeral representation. Accepts value between 1 and 3999 (both inclusive).

  • Create a lookup list containing tuples in the form of (roman value, integer).
  • Use a for loop to iterate over the values in lookup.
  • Use divmod() to update num with the remainder, adding the roman numeral representation to the result.
def to_roman_numeral(num):
  lookup = [
    (1000, 'M'),
    (900, 'CM'),
    (500, 'D'),
    (400, 'CD'),
    (100, 'C'),
    (90, 'XC'),
    (50, 'L'),
    (40, 'XL'),
    (10, 'X'),
    (9, 'IX'),
    (5, 'V'),
    (4, 'IV'),
    (1, 'I'),
  ]
  res = ''
  for (n, roman) in lookup:
    (d, num) = divmod(num, n)
    res += roman * d
  return res
to_roman_numeral(3) # 'III'
to_roman_numeral(11) # 'XI'
to_roman_numeral(1998) # 'MCMXCVIII'

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