plus-one-solution.go

// Recursive One
func plusOne(digits []int) []int {
	lastIndex := len(digits) - 1
	n := digits[lastIndex] + 1

	if (n < 10) {
		digits[lastIndex] = n
		return digits
	}

	r := n / 10
	n = n % 10
	digits[lastIndex] = n

	return plusOneRecursive(digits, lastIndex-1, r)
}

func plusOneRecursive(digits []int, lastIndex int, r int) []int {
	if lastIndex < 0 {
		fmt.Println(lastIndex, r)
		if r != 0 {
			digits = append([]int{r}, digits... )
		}
		return digits
	}
	n := digits[lastIndex] + r
	if n < 10 {
		digits[lastIndex] = n
		return digits
	}

	remainder := n / 10
	newN := n % 10
	
	digits[lastIndex] = newN
	return plusOneRecursive(digits, lastIndex-1, remainder)
}


// Loop
func plusOne(digits []int) []int { 
	carry := 1

	for i:=len(digits)-1; i>=0; i-- {
		sum := carry + digits[i]
		if sum <= 9 {
			digits[i] = sum
			carry = 0
			break
		}

		digits[i] = sum - 10
		carry = 1
	}

	if carry == 1 {
		digits = append([]int{1}, digits...)
	}
	return digits
}