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> result;

        int i=0;

        result.push_back(1);

        for(int i=1;i<=rowIndex;i++)

        {

            vector<int> v=result;

            for(int j=1;j<i;j++) v[j]=result[j]+result[j-1];

            v.push_back(1);

            result=v;

        }

        return result;

    }

};