260. Single Number III

https://leetcode.com/problems/single-number-iii

Python

Defaultdict

from collections import defaultdict
class Solution:

    def singleNumber(self, nums: List[int]) -> List[int]:
        counters = defaultdict(lambda: 0)

        for num in nums:
            counters[num] += 1

        return [num for num, count in counters.items() if count < 2]

Set

class Solution:
    def singleNumber(self, nums: List[int]) -> List[int]:
        memory = set()

        for num in nums:
            if num not in memory:
                memory.add(num)
                continue

            memory.remove(num)

        return memory.pop(), memory.pop()