void quickSort(int[] arr, int begin, int end) {
        if (begin >= end) {
            return;
        }
        int key = arr[begin];
        int i = begin;
        int j = end;
        while (i < j) {
            while (i < j){
                if(arr[j] < key) {
                    arr[i++] = arr[j];
                    break;
                }
                j--;
            }
            while (i < j){
                if(arr[i] > key) {
                    arr[j] = arr[i];
                    break;
                }
                i++;
            }
        }
        arr[i] = key;
        quickSort(arr, begin, i - 1);
        quickSort(arr, i + 1, end);
    }