Problem URL: Find all lonely numbers in the array

We will count the occurrences of each number in the array and return the numbers that have only one occurrence and no adjacent number is present in the list.

class Solution:
    def findLonely(self, nums: List[int]) -> List[int]:
        count = collections.Counter(nums)
        res = []
        for num, cnt in count.items():
            if cnt == 1 and num+1 not in count and num-1 not in count:
                res.append(num)
        return res         

Time complexity: O(n), n is the length of the array
Space complexity: O(n)