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(rowIndex+1);
        result[0] = 1;
        for(int i=1;i<=rowIndex;i++){
            for(int j=i;j>0;j--){
                if(j == i){
                    result[j] = result[j-1];
                }else{
                    result[j] = result[j] + result[j-1];
                }
            }
        }
        return result;
    }
};