标签:leetcode pascals triangle pas
Pascal‘s Triangle:
Given numRows, generate the first numRows of Pascal‘s triangle.
For example, given numRows = 5,
Return
[ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1] ]
Pascal‘s Triangle||:
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?
Pascal‘s triangle.
public class Solution { public List<List<Integer>> generate(int numRows) { if(numRows == 0){ return new ArrayList<List<Integer>>(); } List<List<Integer>> ans = new ArrayList<List<Integer>>(); ans.add(new ArrayList<Integer>(Arrays.asList(1))); for(int i=1;i<numRows;i++){ List<Integer> list = new ArrayList<Integer>(); for(int j=0;j<=i;j++){ if(j==0||j==i){ list.add(1); continue; } list.add(ans.get(i-1).get(j-1)+ans.get(i-1).get(j)); } ans.add(list); } return ans; } }
Pascal‘s Triangle||:
public class Solution { public List<Integer> getRow(int rowIndex) { List<Integer> ans = new ArrayList<Integer>(); for(int i=0;i<=rowIndex;i++){ List<Integer> temp = new ArrayList<Integer>(); for(int j=0;j<=i;j++){ if(j==0||j==i){ temp.add(1); continue; } temp.add(ans.get(j)+ans.get(j-1)); } ans = new ArrayList<Integer>(temp); } return ans; } }
其实这些基本处理就是学习C语言时的杨辉三角。
Pascal's Triangle Pascal's Triangle||
标签:leetcode pascals triangle pas
原文地址:http://blog.csdn.net/huruzun/article/details/39483083