[leetcode]Plus One

简单题。进位加法，或者数九就可以了。

public class Solution {

    public int[] plusOne(int[] digits) {

        // Start typing your Java solution below

        // DO NOT write main() function

        int[] ret = digits;

        int len = digits.length;

        if (len == 0) return ret;

        

        int i = len - 1;

        while (i >= 0 && digits[i] == 9) {

            i--;

        }

        if ( i == -1) {

            ret = new int[len+1];

            ret[0] = 1;

        }

        else {

            digits[i]++;

            for (int j = i+1; j < len; j++) {

                digits[j] = 0;

            }

        }

        

        return ret;

    }

}