66 - 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.

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思路解析：

本题不难理解。在题意上纠结了五分钟。其实就是一个数字，其中的每一位是数组中的每一个元素。

class Solution {
public:
    vector<int> plusOne(vector<int>& digits) 
    {
        if (digits[digits.size() - 1] != 9)
        {
            digits[digits.size() - 1] ++;
            return digits;
        }
        else
        {
            digits[digits.size() - 1] = 0;
            int carry = 1;
            
            for (int i = digits.size() - 2; i >=0; i--)
            {
                if (digits[i] != 9)
                {
                    digits[i]++;
                    return digits;
                }
                else
                {
                    digits[i] = 0;
                }
            }
            
            //都是9的情况
            vector<int> res(digits.size() + 1, 0);
            res[0] = 1;
            return res;
        }
    }
};