15. 3Sum

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

        Arrays.sort(nums);

        for(int i=0;i<n-2;i++)
        {
            if(i>0 && nums[i]==nums[i-1]) continue;

            int j=i+1, k=n-1;

            while(j<k)
            {
                int sum=nums[i]+nums[j]+nums[k];
                if(sum>0)
                {
                    k--;
                }
                else if(sum<0)
                {
                    j++;
                }
                else
                {
                    result.add(Arrays.asList(nums[i],nums[j],nums[k]));
                    k--;
                    j++;

                    while(k>j && nums[k]==nums[k+1])k--;
                    while(k>j && nums[j]==nums[j-1])j++;
                }
            }
        }
        return result;
    }
}v