编程开发Pascal's Triangle解析

编程开发Pascal's Triangle解析，GivennumRows, generate the firstnumRowsof Pascal's triangle.

For example, givennumRows= 5,
Return

[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

class Solution {
    public List<>> generate(int numRows) {
        List list = new ArrayList<>();
        List<>> llist = new ArrayList<>();
        if (numRows == 0){
            return llist;
        }
        for (int i = 1; i <= numRows; ++ i){
            for (int j = 0; j < i; ++ j){
                if (j == 0){
                    list.add(1);
                }
                else if (j == i - 1){
                    list.add(1);
                }
                else {
                    List tmp = llist.get(i-2);
                    list.add(tmp.get(j - 1) + tmp.get(j));
                }
            }
            llist.add(list);
            list = new ArrayList<>();
        }
        return llist;
    }
}