Pascal's Triangle II:節省空間楊輝三角
阿新 • • 發佈:2019-02-18
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?
寫了這麼長久就知道還得練.....下面是更省空間的。class Solution { public List<Integer> getRow(int rowIndex) { if(rowIndex < 0) return new ArrayList<Integer>(); ArrayList<Integer> res = new ArrayList<Integer>(); res.add(1); if(rowIndex == 0){ return res; } ArrayList<Integer> temp = new ArrayList<Integer>(); for(int i = 0;i < rowIndex;i++){ temp.clear(); temp.add(1); for(int j = 0;j< res.size()-1;j++){ temp.add(res.get(j)+res.get(j+1)); } temp.add(1); res.clear(); res.addAll(temp); } return res; } }
public List<Integer> getRow(int rowIndex) { List<Integer> list = new ArrayList<Integer>(); if (rowIndex < 0) return list; for (int i = 0; i < rowIndex + 1; i++) { list.add(0, 1); for (int j = 1; j < list.size() - 1; j++) { list.set(j, list.get(j) + list.get(j + 1)); } } return list; }