Plus one

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

The digits are stored such that the most significant digit is at the head of the list.

Tips: 从数组的最后一位开始运算，先赋值原数组。遇到需要进位从而比原数组多一位的情况，记得重建数组。

代码：

public class Solution {
    public int[] plusOne(int[] digits) {
        int carry = 1;
        for (int i = digits.length - 1; i >= 0 && carry > 0; i--) {
            int sum = digits[i] + carry;
            digits[i] = sum % 10;
            carry = sum / 10;
        }
        if (carry == 0) {
            return digits;
        }
        int[] result = new int[digits.length + 1];
        result[0] = carry;
        for (int i = 0; i < digits.length; i++) {
            result[i + 1] = digits[i];
        }
        return result;
    }
}