leetcode—Plus One

Given a non-negative integer represented as a non-empty array of digits, plus one to the integer.
You may assume the integer do not contain any leading zero, except the number 0 itself.
The digits are stored such that the most significant digit is at the head of the list.

class Solution {
    public int[] plusOne(int[] digits) {
        if(digits==null || digits.length<=0) return digits;
        int i=digits.length-1;
        while(i>=0 && digits[i]==9){
            digits[i] = 0;
            i--;
        }
        if(i<0){
            int[] res = new int[digits.length+1];
            res[0] = 1;
            return res;
        }
        digits[i] = digits[i]+1;
        return digits;
    }
}

这里的关键点就是处理进位，数字的元素是高位在数组的开头，低位在数组的末尾，对数字进行加1，如果当前数组元素为9，则当前位置为0，产生进位，循环到某一位的元素小于9，在该位置的元素加1即可，如果真个数组所有的元素全部为9，则需要新建一个数组长度增1的数组