vector<int> plusOne(vector<int> &digits) {

int carry = 1;

vector<int> res(digits.size());

for (int i = digits.size()-1; i >=0; --i) {

res[i] = (digits[i] + carry) %10;

carry = (digits[i] + carry)/10;

}

if (carry >0) res.insert(res.begin(), carry);

return res;

}