package LeetCode; import java.util.Arrays; import java.util.LinkedList; import java.util.List; public class KSum { public static List> fourSum(int[]nums,int target){ List> res=new LinkedList<>(); if (nums==null||nums.length==0){ return res; } Arrays.sort(nums); res=kSum(4,nums,0,target); return res; } public static List> kSum(int k,int[] nums,int startIndex,int target){ //保存结果 List> res=new LinkedList<>(); //不能够再进行增加了 if(k>nums.length-startIndex){ return res; } if(k==2){ int i=startIndex,j=nums.length-1; while(i temp=new LinkedList<>(); temp.add(nums[i]); temp.add(nums[j]); res.add(temp); while(istartIndex && nums[i]==nums[i-1]){ continue; } List>tempList=kSum(k-1,nums,i+1,target-nums[i]); for(List temp:tempList){ //每一次的添加nums[i] temp.add(0,nums[i]); //添加到最终的结果中去 res.add(temp); } } return res; } } public static void main(String[] args){ int[] nums={1,0,-1,0,-2,2}; int target=0; List> res=fourSum(nums,target); System.out.println(res); } }