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?
public class Solution { public ArrayList<Integer> getRow(int rowIndex) { ArrayList<Integer> resultList = new ArrayList<Integer>(); if (rowIndex == 0) { resultList.add(1); return resultList; } // Initial resultList.add(1); resultList.add(1); for (int i = 2; i <= rowIndex; i++) { resultList.add(1, resultList.get(0) + resultList.get(1)); for (int j = 2; j < resultList.size() - 1; j++) { resultList.set(j, resultList.get(j) + resultList.get(j + 1)); } } return resultList; } }
learned: process: [1,2,1] -> [1,3,2,1] - > [1,3,(2+1),1]