public static List<Integer> quickSort(List<Integer> arr) {
    // Write your code here
    int n = arr.size();
    List<Integer> left = new ArrayList<>();
    List<Integer> right = new ArrayList<>();
    List<Integer> equal = new ArrayList<>();
    int p = arr.get(0);
    for(int i = 0; i < n; i++) {
        if(p > arr.get(i)) {
            left.add(arr.get(i));
        } else if (p < arr.get(i)) {
            right.add(arr.get(i));
        } else {
            equal.add(arr.get(i));
        }
    }
    List<Integer> result = new ArrayList<>();
    result.addAll(left);
    result.addAll(equal);
    result.addAll(right);
    return result;
    }