public List<List<Integer>> fourSum(int[] numbers, int target) {
        // write your code here
        Arrays.sort(numbers);
        List<List<Integer>> list = new ArrayList<>();
        int i = 0,j=0;
        for(i=0;i<numbers.length-3;i++){
            j=i+1;
            while
 
(j<numbers.length-2){ 
             int left = j+1,right = numbers.length-1;
             while(left<right){
             int sum =    numbers[i]+numbers[j]+numbers[left]+numbers[right];
             if(sum==target){
                 list.add(Arrays.asList(numbers[i],numbers[j],numbers[left++],numbers[right--]));
                 while
 
(left<right&&numbers[left]==numbers[left-1]){
                     ++left;
                 }
                 while(left<right&&numbers[right]==numbers[right+1]){
                     --right;
                 }

             }else if(sum<target){
                 ++left;
             }else
 
{
                 --right;
             }
          } 
          while(numbers[j]==numbers[++j]&&j<numbers.length-1);
            }
             while(i<numbers.length-1&&numbers[i]==numbers[i+1]){
                 i++;
             }
        }
        return list;
    }