考查，最高位有进位

 1 class Solution {
 2 public:
 3     vector<int> plusOne(vector<int> &digits) {
 4         // IMPORTANT: Please reset any member data you declared, as
 5         // the same Solution instance will be reused for each test case.
 6         int i;
 7         int n=digits.size();
 8         if(n==0)
 9             return digits;
10         int mod=1;
11         for(i=n-1;i>=0;--i)
12         {
13             digits[i]+=mod;
14             mod=digits[i]/10;
15             digits[i]=digits[i]%10;
16             
17         }
18         if(mod!=0)
19             digits.insert(digits.begin(),mod);
20         return digits;
21     }
22 };