leetcode_Plus One

描述：

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.

思路：

很简单的字符串加法，当然要考虑到最后的进位

代码：

public int[] plusOne(int[] digits) {
        if(digits==null||digits.length==0)
            return digits;
        int len=digits.length;
        int flowNum=1;
        int sum=0;
        for(int i=len-1;i>=0;i--)
        {
            sum=digits[i]+flowNum;//the first time flowNum is the addNum 1
            digits[i]=sum%10;
            flowNum=sum/10;
        }
        if(flowNum!=0)
        {
            int newArr[]=new int[len+1];
            newArr[0]=flowNum;
            for(int i=1;i<newArr.length;i++)
                newArr[i]=digits[i-1];
            return newArr;
        }
        return digits;
    }