18. 4Sum

class Solution {
    public List<List<Integer>> fourSum(int[] nums, int target) {
        List<List<Integer>>ll=new ArrayList<>();
        int n=nums.length;
        Arrays.sort(nums);
        for(int i=0;i<n-3;i++){
            for(int j=i+1;j<n-2;j++){
                int l=j+1,r=n-1;
                while(l<r){
                    long sum=(long)nums[i]+nums[j]+nums[l]+nums[r];
                    if(sum==target&&!ll.contains(Arrays.asList(nums[i],nums[j],nums[l],nums[r]))){
                        ll.add(Arrays.asList(nums[i],nums[j],nums[l],nums[r]));
                        l++;
                        r--;
                }else if(sum<target){
                    l++;
                }else{
                    r--;
                }
                }
                
                }
                }
        return ll;
    }
}