118. Pascal's Triangle（暴力求解法）

Input: 5
Output:
[
     [1],
    [1,1],
   [1,2,1],
  [1,3,3,1],
 [1,4,6,4,1]
]

class Solution {
    public List<List<Integer>> generate(int numRows) {
        List<List<Integer>> res = new ArrayList<>();
        if (numRows <= 0) return res;
        List<Integer> list = new ArrayList<>();
        for (int i = 1; i <= numRows; i++) {
            list.add(1);
            for (int j = list.size() - 2; j > 0; j--) {
                list.set(j, list.get(j) + list.get(j - 1));
            }
            res.add(new ArrayList<>(list));
        }
        return res;
    }
}