class Solution {
    public int[] plusOne(int[] digits) {
        for (int i = digits.length-1; i >= 0; i--) {
            if (digits[i] != 9) {
                digits[i]++;
                return digits;
            }
            digits[i] = 0;
        }
        //跳转for循环，说明数字全部都是9
        int[] result = new int[digits.length+1];
        result[0] = 1;
        return result;
    }
}