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?

Solution

public class Solution {
    public List<Integer> getRow(int num) {
        int numRows = num + 1;

              if (numRows < 1) return new ArrayList<>();

        List<Integer> cur = new ArrayList<>();
        cur.add(1);

        List<Integer> cur1 = new ArrayList<>();
        cur1.add(1);
        cur1.add(1);

        List<List<Integer>> result = new ArrayList<>();
        result.add(cur);
        result.add(cur1);

        if (numRows == 1) {
            return cur;
        } else if (numRows == 2) {
            return cur1;
        } else {

            for (int i = 3; i <= numRows; i ++) {
                List<Integer> prev = result.get(i-2);

                List<Integer> newResult = new ArrayList<>();
                newResult.add(1);
                for(int j = 1; j < i -1; j ++) {
                    newResult.add(prev.get(j-1) + prev.get(j));
                }
                newResult.add(1);
                result.add(newResult);
            }
        }

        return result.get(result.size()-1);
    }
}