Pascal's Triangle II

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?

k是从0开始的，第1行是[1,1]，之后从后向前计算上一行两个数的和。

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