integer-to-roman.md

Code

func getNum(digit int, letters []string) string {
	if digit > 0 && digit < 5 {
		if digit == 4 {
			return letters[0] + letters[1]
		} else {
			return strings.Repeat(letters[0], digit)
		}
	} else if digit == 5 {
		return letters[1]
	} else if digit > 5 && digit < 9 {
		return letters[1] + strings.Repeat(letters[0], digit-5)
	} else if digit == 9 {
		return letters[0] + letters[2]
	}

	return ""
}

func intToRoman(num int) string {
	base := 1
	sol := ""
	for num > 0 {
		digit := num % 10
		num = num / 10

		switch base {
		case 1:
			sol = getNum(digit, []string{"I", "V", "X"}) + sol
		case 10:
			sol = getNum(digit, []string{"X", "L", "C"}) + sol
		case 100:
			sol = getNum(digit, []string{"C", "D", "M"}) + sol
		case 1000:
			sol = getNum(digit, []string{"M", " ", " "}) + sol
		}

		base = base * 10
	}

	return sol
}

Alternatively

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

	return M[num/1000] + C[(num%1000)/100] + X[(num%100)/10] + I[num%10]
}

Solution in mind

• Iterate through each digit in the number and get appropriate letter for the number.

• The letter is determined by the digit and the base (unit's place, ten's place, etc.).

• Concatenation of these letters gives us the required answer.