from collections import defaultdict

class Solution:
    def threeSum(self, nums):
        """
        :type nums: List[int]
        :rtype: List[List[int]]
        """
        nums.sort()
        d=defaultdict(int)
        s=defaultdict(int)
        solution=[]
        for x in nums:
            d[x]+=1
        
        for i,first in enumerate(nums):
            d[first]-=1
            if first >0:
                break
            if i>0 and nums[i] == nums[i-1]:
                continue
            for j,second in enumerate(nums[i+1:]):#range(i+1,len(nums)):

                if -first-second == second:
                    if d[-first-second]-1 > 0 and -first-second >= second:
                        if  s[first,second]==0:
                            solution.append([first,second,-first-second])
                            s[first,second]+=1
                if -first-second != second:
                    if d[-first-second] > 0 and -first-second >= second:
                        if  s[first,second]==0:
                            solution.append([first,second,-first-second])
                            s[first,second]+=1
                        
                
    
        return solution