Pascal’s Triangle

Given numRows, generate the first numRows of Pascal’s triangle.

For example, given numRows = 5,
Return

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

Solution:

public class Solution {
  public List<List<Integer>> generate(int numRows) {
    List<List<Integer>> res = new ArrayList<List<Integer>>();
    for (int i = 0; i < numRows; i++) {
      List<Integer> list = new ArrayList<Integer>(Arrays.asList(1));
      for (int j = 1; j < i; j++) {
        list.add(res.get(i - 1).get(j - 1) + res.get(i - 1).get(j));
      }
      if (i > 0) list.add(1);
      res.add(list);
    }
    return res;
  }
}