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