public void quickSortByX(Point[] arr, int begin, int end) {
        if (begin < end) {
            int partitionIndex = partition(arr, begin, end);
            quickSortByX(arr, begin, partitionIndex - 1);
            quickSortByX(arr, partitionIndex + 1, end);
        }
    }

    private int partition(Point[] arr, int begin, int end) {
        Point pivot = arr[end];
        int i = (begin-1);

        for (int j = begin; j < end; j++) {
            if (arr[j].x <= pivot.x) {
                i++;

                Point swapTemp = arr[i];
                arr[i] = arr[j];
                arr[j] = swapTemp;
            }
        }

        Point swapTemp = arr[i+1];
        arr[i+1] = arr[end];
        arr[end] = swapTemp;

        return i+1;
    }