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] ]
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;
}
}