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export const MIN_ARABIC_TO_ROMAN = 1;
export const MAX_ARABIC_TO_ROMAN = 3999;
export function arabicToRoman(num: number) {
if (num < MIN_ARABIC_TO_ROMAN || num > MAX_ARABIC_TO_ROMAN) {
return '';
}
const lookup: { [key: string]: number } = {
M: 1000,
CM: 900,
D: 500,
CD: 400,
C: 100,
XC: 90,
L: 50,
XL: 40,
X: 10,
IX: 9,
V: 5,
IV: 4,
I: 1,
};
let roman = '';
for (const i in lookup) {
while (num >= lookup[i]) {
roman += i;
num -= lookup[i];
}
}
return roman;
}
const ROMAN_NUMBER_REGEX = /^M{0,3}(CM|CD|D?C{0,3})(XC|XL|L?X{0,3})(IX|IV|V?I{0,3})$/;
export function isValidRomanNumber(romanNumber: string) {
return ROMAN_NUMBER_REGEX.test(romanNumber);
}
export function romanToArabic(s: string) {
if (!isValidRomanNumber(s)) {
return null;
}
const map: { [key: string]: number } = { I: 1, V: 5, X: 10, L: 50, C: 100, D: 500, M: 1000 };
return [...s].reduce((r, c, i, s) => (map[s[i + 1]] > map[c] ? r - map[c] : r + map[c]), 0);
}
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