3Sum

public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> res = new LinkedList<>();
        if (nums == null || nums.length < 3) {
            return res;
        }
        Arrays.sort(nums);
        for (int i = 0; i < nums.length - 2; i++) {
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            int left = i + 1, right = nums.length - 1;
            while (left < right) {
                int sum = nums[i] + nums[left] + nums[right];
                if (sum == 0) {
                    List<Integer> list = new LinkedList<>();
                    list.add(nums[i]);
                    list.add(nums[left]);
                    list.add(nums[right]);
                    res.add(list);
                    left++;
                    right--;
                    while(nums[left] == nums[left - 1] && left < right) {
                        left++;
                    }
                    while(nums[right] == nums[right + 1] && left < right) {
                        right--;
                    }
                } else if (sum < 0) {
                    left++;
                } else {
                    right--;
                }
            }
        }
        return res;
    }