public static List<Integer> closestNumbers(List<Integer> arr) {
        if (arr == null || arr.isEmpty()) return new ArrayList<>();
        if (arr.size() == 1) return arr;
        
        Collections.sort(arr);
        Map<Integer, List<Integer>> map = new HashMap<>();
        int min = Integer.MAX_VALUE, diff = 0;
        
        for (int i=1;i<arr.size();i++) {
            diff = arr.get(i) - arr.get(i-1);
            min = Math.min(min, diff);
            
            if (!map.containsKey(diff))
                map.put(diff, new ArrayList<>());
            map.get(diff).add(arr.get(i-1));
            map.get(diff).add(arr.get(i));
        }
        
        return map.get(min);
    }

public static List<int> closestNumbers(List<int> arr)
    {
        arr.Sort();
        List<int> res = new();
        
        int diff = int.MaxValue;
        
        for(int i = 0; i < arr.Count-1; i++)
        {
            int temp = Math.Abs(arr[i] - arr[i+1]);
            
            if(temp < diff)
            {
                diff = temp;
                res.Clear();
            }
            
            if(temp == diff)
            {
                res.Add(arr[i]);
                res.Add(arr[i+1]);
            }   
        }
        
        return res;
    }

    public static List<Integer> closestNumbers(List<Integer> arr) {
        arr.sort((a,b) -> a.compareTo(b));
        int minDiff = Integer.MAX_VALUE;
        for(int i=1;i<arr.size();i++) minDiff = Math.min(minDiff,  arr.get(i) - arr.get(i-1));
        List<Integer> res = new ArrayList<>();
        for(int i=1;i<arr.size();i++) if(arr.get(i) - arr.get(i-1) == minDiff) {
            res.add(arr.get(i-1));
            res.add(arr.get(i));
        } 
        return res;
    }

def closestNumbers(arr):
    arr.sort()
    output = []
    minimum = arr[1] - arr[0]
    for i in range(1, len(arr)): 
        diff = arr[i] - arr[i-1]
        if diff == minimum: 
            output.extend([arr[i-1], arr[i]])
        if diff < minimum: 
            minimum = diff 
            output = [arr[i-1], arr[i]]
    
    return output