3Sum.java

class 3Sum {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        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;
            int right = nums.length-1;

            while(left<right){
                int sum = nums[i]+nums[left]+nums[right];
                if(sum==0){
                    result.add(Arrays.asList(nums[i],nums[left],nums[right]));
                    while(left<right && nums[left] == nums[left+1]){
                        left++;
                    }
                    while(left<right && nums[right] == nums[right-1]){
                        right--;
                    }

                    left++;
                    right--;

                }
                else if(sum<0){
                    left++;
                }
                else{
                    right--;
                }
            }
        }
        return result;

        
    }
}