[leetcode]Plus One

class Solution {public:    vector<int> plusOne(vector<int> &digits) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(digits.empty()) return vector<int>();                int i = digits.size()-1;                while(i >= 0 && digits[i] == 9){            digits[i] = 0;            i--;        }                if(i >= 0) digits[i]++;        else digits.insert(digits.begin(),1);                return digits;            }};