leetcode之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()) {
            digits.push_back(1);
            return digits;
        }
        vector<int> nums(digits.rbegin(), digits.rend());
        vector<int>::iterator itr = nums.begin();
        int carry = 0;
        int sum = carry+*itr+1;
        while (itr != nums.end()) {
            if (sum<10) {
                *itr = sum;
                carry = 0;
                break;
            } else {
                carry = sum/10;
                *itr = sum%10;
            }
            itr++;
            sum = carry+*itr;
        }
        if (carry >0) {
            nums.push_back(carry);
        }
        vector<int> res (nums.rbegin(), nums.rend());
        return res;
    }
};