3Sum

1public List<List<Integer>> threeSum(int[] nums) {
2    List<List<Integer>> result = new ArrayList<>();
3    Arrays.sort(nums);
4
5    for (int i = 0; i < nums.length - 2; i++) {
6        if (i > 0 && nums[i] == nums[i - 1]) {
7            continue;
8        }
9
10        int left = i + 1;
11        int right = nums.length - 1;
12
13        while (left < right) {
14            int sum = nums[i] + nums[left] + nums[right];
15
16            if (sum == 0) {
17                result.add(Arrays.asList(nums[i], nums[left], nums[right]));
18
19                while (left < right && nums[left] == nums[left + 1]) {
20                    left++;
21                }
22                while (left < right && nums[right] == nums[right - 1]) {
23                    right--;
24                }
25
26                left++;
27                right--;
28            } else if (sum < 0) {
29                left++;
30            } else {
31                right--;
32            }
33        }
34    }
35
36    return result;
37}