LeetCode 119 - 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?

public List<Integer> getRow(int rowIndex) {
    List<Integer> list = new ArrayList<>();
    if(rowIndex < 0) return list;
    for(int i=0; i<=rowIndex; i++) {
        list.add(1);
        for(int j=i-1; j>=1; j--) {
            list.set(j, list.get(j)+list.get(j-1));
        }
    }
    return list;
}