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path: root/go/roman-numerals/roman_numerals.go
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package romannumerals

import "errors"

const testVersion = 2

var (
	m0 = []string{"", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"}
	m1 = []string{"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"}
	m2 = []string{"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"}
	m3 = []string{"", "M", "MM", "MMM"}
)

func ToRomanNumeral(n int) (string, error) {
	if n < 1 || n >= 4000 {
		return "", errors.New("out of range")
	}
	return m3[n%1e4/1e3] + m2[n%1e3/1e2] + m1[n%1e2/1e1] + m0[n%1e1], nil
}