[LeetCode] 15. 3Sum

Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.

Note: The solution set must not contain duplicate triplets.

public class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> results = new ArrayList<List<Integer>>();
        if (nums.length < 3) {
            return results;
        }
        Arrays.sort(nums);
        if (nums[0] > 0 || nums[nums.length - 1] < 0) {
            return results;
        }
        for (int i = 0; i < nums.length; i++) {
            if (nums[i] > 0) {
                break;
            }
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            int l = i + 1;
            int r = nums.length - 1;
            while (l < r) {
                int t = nums[i] + nums[l] + nums[r];
                if (t == 0) {
                    List<Integer> list = new ArrayList<Integer>();
                    list.add(nums[i]);
                    list.add(nums[l]);
                    list.add(nums[r]);
                    results.add(list);
                    while (l < r && nums[l + 1] == nums[l]) {
                        l++;
                    }
                    while (l < r && nums[r - 1] == nums[r]) {
                        r--;
                    }
                    l++;
                    r--;
                } else if (t < 0) {
                    l++;
                } else {
                    r--;
                }
            }
        }
        return results;
    }
}