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)
    {
        int len = digits.size();
        int i;
        int a[len+1];
        memset(a,0,sizeof(a));
        int carry = 1;
        for(i=0;i<len;i++)
        {
            a[len-i] += (carry + digits[len-i-1])%10;
            carry     = (carry + digits[len-i-1])/10;
        }
        if(carry == 0)
        {
            for(i=0;i<len;i++)
            digits[i] = a[i+1];
            return digits;
        }
        else
        {
            a[0] = 1;
            for(i=0;i<len;i++)
            digits[i] = a[i];
            digits.push_back(a[len]);
            return digits;
        }
    }
};