3Sum.java

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> output = new LinkedList<>();
        Arrays.sort(nums);
        for(int i=0;i<nums.length-2;i++){
            int low= i+1;
            int high = nums.length-1;
            int sum = 0 - nums[i];
            if(i==0 || (i>0 && nums[i]!=nums[i-1])){
                while(low < high){
                    if(nums[low] + nums[high] == sum){
                        output.add(Arrays.asList(nums[i],nums[low],nums[high]));
                        while((low < high) && nums[low] == nums[low+1])
                        {
                            low++;
                        }
                        while((low < high) && nums[high] ==nums[high -1]){
                            high--;
                        }
                        low++;
                        high--;
                        
                    }
                    else if(nums[low]+nums[high] > sum){
                        high--;
                    }
                    else if(nums[low]+nums[high] < sum){
                        low++;
                    }
                }
            }
        }                return output;

    }
}