3sum.java

import java.util.*;
class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        List<List<Integer>>list = new ArrayList<>();
        for(int i=0; i<nums.length; 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){
                    left++;
                }else if(sum>0){
                    right--;
                }else
                {
                    list.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--;
                }
            }
        }
        return list;
    }
}