def closestNumbers(arr):
    minimium=0
    arr.sort()
    sorted_list=[]
    for index,element in enumerate(arr[:-1]):
        sorted_list.append([element,arr[index+1]])
        minimium = arr[index+1] - element if (minimium > arr[index+1] - element or index==0) else minimium
    return [i for ans in sorted_list if ans[1]- ans[0] == minimium for i in ans]

def closestNumbers(arr):
    dif = []
    arr.sort()
    for i in range(len(arr) - 1):
        dif.append(arr[i+1] - arr[i])
    min_dif = min(dif)
    res = []
    for i in range(len(dif)):
        if dif[i] == min_dif:
            res.append(arr[i])
            res.append(arr[i+1])
    return res

def closestNumbers(arr):
    arr.sort()
    
    result = []
    pre_diff = None
    
    for i in range(len(arr)-1):
        abs_diff = abs((arr[i]) - (arr[i+1]))
        
        if not result  or  abs_diff == pre_diff:
            result.append(arr[i])
            result.append(arr[i+1])
            pre_diff = abs_diff
        elif abs_diff < pre_diff:
            result.clear()

            result.append(arr[i])
            result.append(arr[i+1])
            pre_diff = abs_diff

    return result

public static List<Integer> closestNumbers(List<Integer> arr) {
    if (arr == null || arr.size() < 2) {
        return new ArrayList<>();
    }

    arr.sort(null);
    int smallestDiff = Integer.MAX_VALUE;
    List<Integer> results = new ArrayList<>();

    for (int i = 0; i < arr.size() - 1; i++) {
        int diff = arr.get(i + 1) - arr.get(i);

        if (diff < smallestDiff) {
            results.clear();
            results.add(arr.get(i));
            results.add(arr.get(i + 1));
            smallestDiff = diff;
        } else if (diff == smallestDiff) {
            results.add(arr.get(i));
            results.add(arr.get(i + 1));
        }
    }

    return results;
}

vector<int> closestNumbers(vector<int> arr) {
    sort(arr.begin(), arr.end());
    int diff = INT_MAX;
    vector<int> result;
    for(int i = 1; i < arr.size(); i++){
        if(arr[i] - arr[i-1] < diff){
            diff = arr[i] - arr[i-1];
            result = {arr[i-1], arr[i]};
        }
        else if(arr[i] - arr[i-1] == diff){
            result.insert(result.end(), {arr[i-1], arr[i]});
        }
    }
    return result;
}