66. Plus One

problem：

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.

这道题遍历逢9进1即可，如果最后都是9，就用insert在vector起始处添加1

class Solution {public:    vector<int> plusOne(vector<int>& digits) {        int i;        for(i=digits.size()-1; i >= 0; i--)        {            if(digits[i] !=9)            {                ++digits[i];                return digits;            }            else            {                digits[i] = 0;            }        }        if(i == -1)        {            digits.insert(digits.begin(),1);        }        return digits;    }};