2150. PYTHON Fast Hashmap and If check
class Solution:\n    def findLonely(self, nums: List[int]) -> List[int]:\n        \n        numbers = []\n        \n        seen = {}\n        \n        for num
class Solution:\n    def findLonely(self, nums: List[int]) -> List[int]:\n        \n        numbers = []\n        \n        seen = {}\n        \n        for num in nums:\n            seen[num] = 1 + seen.get(num,0) #Get appearance counter\n            \n            \n        for val in nums:\n            \n            if (val - 1) not in seen and (val + 1) not in seen and seen[val] == 1: #Must appear once.\n                numbers.append(val)\n                \n        return numbers\n    \n    \n        #Time: O(n)\n        #Space: O(n)
['Array']