Plus one to the number

Given a non-negative number represented as an array of digits, plus one to the number.

• Time: O(n)
• Space: O(1)

public int[] plusOne(int[] digits) {
    for (int i = digits.length - 1; i >= 0; i--) {
        if (digits[i] != 9) {
            digits[i]++;
            break;
        } else {
            digits[i] = 0;
        }
    }
    if (digits[0] == 0) {
        int[] res = new int[digits.length + 1];
        res[0] = 1;
        return res;
    }
    return digits;
}