Pascal's Triangle II

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?

class Solution {
public:
    vector<int> getRow(int rowIndex) {
        vector<int> row;
        row.push_back(1);
        if(rowIndex == 0) return row;
        
        row.push_back(1);
        if(rowIndex == 1) return row;
        
        for(int i = 2; i <= rowIndex; i++){
            vector<int> temp;
            temp.push_back(1);
            for(int j = 1; j < i; j++)
                temp.push_back(row[j-1] + row[j]);
            temp.push_back(1);
            row = temp;
        }
        return row;
    }
};