[LeetCode] Pascal's Triangle

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

public class Solution {
public ArrayList<ArrayList<Integer>> generate(int numRows) {
ArrayList<ArrayList<Integer>> list = new ArrayList<ArrayList<Integer>>();

for (int i = 0; i < numRows; i++) {
ArrayList<Integer> rowList = new ArrayList<Integer>();
// add an element
for (int j = 0; j <= i; j++) {
if (j == 0 || j == i) rowList.add(1);
else rowList.add(list.get(i-1).get(j-1) + list.get(i-1).get(j));
}

// add a row
list.add(rowList);
}

return list;
}
}