public class Solution {
  public List<List<Integer>> threeSum(int[] nums) {
    List<List<Integer>> result = new ArrayList<>();
    if (nums.length < 2) {
      return result;
    }

    Arrays.sort(nums);
    for (int i = 0; i < nums.length - 2; i++) {
        if
 
 (i > 0 && nums[i] == nums[i - 1]) {
            continue;
        }
      int j = i + 1;
      int k = nums.length - 1;
      while (j < k) {
        if (nums[i] + nums[j] + nums[k] == 0) {
          result.add(Arrays.asList(nums[i], nums[j++], nums[k--]));
            while (j < k && nums[j] == nums[j - 1]) j++;
                
 
while (j < k && nums[k] == nums[k + 1]) k--;
        } else if (nums[i] + nums[j] + nums[k] > 0) {
          k--;
        } else {
          j++;
        }
      }
    }
    return result;
  }
}

LeetCode 15: 3 Sum