https://leetcode.com/problems/plus-one/

题目：

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：

设置进1位，逢9进1。注意999这种情况要首位insert1。

 1 class Solution {
 2 public:
 3     vector<int> plusOne(vector<int>& digits) {
 4         int n=digits.size();
 5         bool jinyi=false;
 6         for(int i=n-1;i>=0;i--){
 7             if(digits[i]==9){
 8                 digits[i]=0;
 9                 jinyi=true;
10             }
11             else{
12                 digits[i]++;
13                 jinyi=false;
14                 break;
15             }
16         }
17         if(jinyi==true){
18             vector <int>::iterator theIterator = digits.begin(); 
19             digits.insert(theIterator,1,1);
20         }
21         return digits;
22     }
23 };