[C#], Counter
\npublic class Solution {\n    public IList<int> FindLonely(int[] nums) {\n        var res = new List<int>();\n        var map = new Dictionary<int, int>();\n  
```\npublic class Solution {\n    public IList<int> FindLonely(int[] nums) {\n        var res = new List<int>();\n        var map = new Dictionary<int, int>();\n        for (int i = 0; i < nums.Length; i++) {\n            map[nums[i]] = map.GetValueOrDefault(nums[i], 0) + 1;\n        }\n\n        for (int i = 0; i < nums.Length; i++) {\n            if (map[nums[i]] == 1 && !(map.ContainsKey(nums[i] + 1) || map.ContainsKey(nums[i] - 1))) {\n                res.Add(nums[i]);\n            }\n        }\n        return res;\n    }\n}\n```
[]