2150. Find All Lonely Numbers in the Array - LeetCode Solution

from collections import defaultdict
class Solution:
    def findLonely(self, nums: List[int]) -> List[int]:
        check = defaultdict(int)
        for i in nums:
            check[i] += 1
        ans = []
        for i in nums:
            if ((i==0) or (i>=1 and check[i-1]==0)):
                if check[i]==1 and check[i+1]==0:
                    ans.append(i)
        return ans