3Sum using a dictionary

3Sum.py

class Solution:
    def threeSum(self, nums):
        if all(map(lambda x: x == 0, nums)):
            if len(nums) >= 3:
                return [[0,0,0]]
            else:
                return []
        
        positives = [x for x in nums if x > 0]
        negatives = [x for x in nums if x <= 0]
        
        positives_set = set(positives)
        negatives_set = set(negatives)
        
        ret = set()
        
        if nums.count(0) >= 3:
            ret.add((0,0,0))
        
        for i in range(len(positives)):
            for j in range(len(positives)):
                if i == j:
                    continue
                
                if 0 - (positives[i] + positives[j]) in negatives_set:
                    ret.add(tuple(sorted((0 - (positives[i] + positives[j]), positives[i], positives[j]))))
        
        for i in range(len(negatives)):
            for j in range(len(negatives)):
                if i == j:
                    continue
                
                if 0 - (negatives[i] + negatives[j]) in positives_set:
                    ret.add(tuple(sorted((0 - (negatives[i] + negatives[j]), negatives[i], negatives[j]))))
        return [ list(x) for x in ret ]