Method fourSum

src/com/blankj/medium/_0018/Solution.java:57–64

(int[] nums, int target)

//    }

    public List<List<Integer>> fourSum(int[] nums, int target) {
        Arrays.sort(nums);
        int len = nums.length;
        if (len < 4) return Collections.emptyList();
        int max = nums[len - 1];
        if (4 * max < target) return Collections.emptyList();
        return kSum(nums, 0, 4, target);
    }

    private List<List<Integer>> kSum(int[] nums, int start, int k, int target) {
        List<List<Integer>> res = new ArrayList<>();