Pascal's Triangle II

Given an index k, return the k^th row of the Pascal's triangle.

For example, given k = 3,
Return [1,3,3,1].

Note:
Could you optimize your algorithm to use only O(k) extra space?

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<int> result;
        if (rowIndex < 0)
        {
            return result;
        }

        result.push_back(1);
        for (int i = 1; i <= rowIndex; i++)
        {
            int temp = 1;
            for (int j = 1; j < i; j++)
            {
                int val = temp + result[j];
                temp = result[j];
                result[j] = val;
            }
            result.push_back(1);
        }

        return result;
    }
};