package LeetCode; import java.util.ArrayList; import java.util.List; public class Combinations { private static List> res=new ArrayList<>(); public static List>combine(int n,int k){ helper(n,1,k,new ArrayList<>()); return res; } public static void helper(int n,int start,int k,ListsumList){ if (k==0){ res.add(new ArrayList<>(sumList)); } //注意这里的长度:终点-起点+1 if(k<0||n-start+1> result=combine(4,3); System.out.println(result); } }