标签:extra temp solution line color example long esc ++
Description:
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?
My Solution:
class Solution { public List<Integer> getRow(int rowIndex) { List list = new ArrayList(); for(int i = 0;i <= rowIndex;i++){ List<Integer> line = new ArrayList<Integer>(); for(int j = 0;j <= i;j++){ if(j == 0 || j== i){ line.add(1); }else{ List<Integer> temp = (ArrayList<Integer>)list.get(list.size() - 1); line.add(temp.get(j - 1) + temp.get(j)); } } list.add(line); } return (ArrayList<Integer>)list.get(list.size() - 1); } }
Better Solution:
class Solution { public List<Integer> getRow(int rowIndex) { rowIndex+=1; int[][] res=new int[rowIndex][]; List<Integer> RES=new ArrayList<>(); for(int i=0;i<rowIndex;i++){ res[i]=new int[i+1]; for(int j=0;j<i+1;j++){ if(j==0||j==i)res[i][j]=1; else res[i][j]=res[i-1][j-1]+res[i-1][j]; if(i==rowIndex-1)RES.add(res[i][j]); } } return RES; } }
Best Solution:
class Solution { public List<Integer> getRow(int rowIndex) { List<Integer> result=new ArrayList<Integer>(); for(int k=0,value=1;k<=rowIndex;k++){ result.add(value); //核心 value=(int)((long)value*(rowIndex-k)/(k+1)); } return result; } }
标签:extra temp solution line color example long esc ++
原文地址:http://www.cnblogs.com/kevincong/p/7900348.html