"""

Roman Numeral to Integer

Given a Roman numeral string, convert it to an integer. Input is guaranteed

to be within the range from 1 to 3999.

Reference: https://en.wikipedia.org/wiki/Roman_numerals

Complexity:

Time: O(n) where n is the length of the Roman numeral string

Space: O(1)

"""

from __future__ import annotations

def roman_to_int(text: str) -> int:

"""Convert a Roman numeral string to an integer.

Args:

text: A valid Roman numeral string.

Returns:

The integer value of the Roman numeral.

Examples:

>>> roman_to_int("DCXXI")

621

"""

number = 0

roman_values = {

"M": 1000,

"D": 500,

"C": 100,

"L": 50,

"X": 10,

"V": 5,

"I": 1,

}

for index in range(len(text) - 1):

if roman_values[text[index]] < roman_values[text[index + 1]]:

number -= roman_values[text[index]]

else:

number += roman_values[text[index]]

return number + roman_values[text[-1]]