[LeetCode] Plus One

Given a number represented as an array of digits, plus one to the number.

class Solution {
public:
    vector<int> plusOne(vector<int> &digits) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int a = 1;
        vector<int> ans;
        vector<int>::iterator it;
        for(int i = digits.size() - 1;i >= 0;i--)
        {
            it = ans.begin();
            int b = (a + digits[i]) % 10;
            a = (a + digits[i]) / 10;
            ans.insert(it, b);
        }
        if(a != 0)
        {
            it = ans.begin();
            ans.insert(it, a);
        }
        
        return ans;
    }
};