Given a non-negative index k where k ≤ 33, return the kth index row of the Pascal's triangle.

Note that the row index starts from 0.


Input:  rowIndex = 3

Output:[1,3,3,1]//means want the fourth row

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