Pascal's Triangle II

Description:

Given an index k, return the kth 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?

Code:

  vector<int> getRow(int rowIndex) {
        vector<int>lastRow;
        vector<int>cur;
        
        if (rowIndex >= 0)
        {
            cur.push_back(1);
            lastRow = cur;
            
            for (int i = 1; i <= rowIndex; ++i)
            {
                cur.clear();
                for (int j = 0; j <= i; ++j)
                {
                    if (j == 0)
                        cur.push_back(lastRow[0]);
                    else if (j==lastRow.size())
                        cur.push_back(lastRow[j-1]);
                    else
                        cur.push_back(lastRow[j]+lastRow[j-1]);
                }
                lastRow = cur;
            }
        }
        return lastRow;
    }