Leetcode Pascal's Triangle II

Pascal's Triangle II Oct 29 '12
Given an index k, return the kth row of the Pascal's triangle.

For example, given k = 3,
Return [1,3,3,1].

Note:
Could you optimize your algorithm to use only O(k) extra space?

Leetcode Pascal's Triangle II.java

public class Solution {
    public ArrayList<Integer> getRow(int rowIndex) {
        // Start typing your Java solution below
        // DO NOT write main() function
        ArrayList<Integer> lastLine = new ArrayList<Integer>();
        lastLine.add(1);
        
        if(rowIndex == 0) return lastLine;
        
        ArrayList<Integer> thisLine = new ArrayList<Integer>();
        
        for(int i = 1; i <= rowIndex; i++){
            for(int j = 0; j <= i; j++){
                if(j == 0) thisLine.add(1);
                else if(j < i){
                    thisLine.add(lastLine.get(j - 1) + lastLine.get(j));
                }
                else if(j == i){
                    thisLine.add(1);
                }
            }
            lastLine = thisLine;
            thisLine = new ArrayList<Integer>(); 
        }
        return lastLine;
        
    }
}