public static void shellSort(int[] data) {  
        for(int gap = data.length / 2; gap > 0; gap /= 2){
            for(int i = gap; i < data.length; i++){
                int tmp = data[i];
                int j;
                for(j = i; j >= gap && tmp < data[j - gap]; j -= gap){
                    data[j] = data[j-gap];
                }
                data[j] = tmp;
            }
        }
    }