void ShellSort(int* data ,int length)
{
    if( data == NULL || length <= 0 )
        return;

    int d = length/2;  //步長
    while( d )
    {
        for(int i = 0 ; i < d ; ++i) //根據步長分成組，對每組進行插入排序
        {
            //插入排序
            for(int j = i+d; j <length ; j +=d )
            {
                if( data[j] < data[j -d])
                {
                    int temp = data[j]; //哨兵
                    int k = j-d;
                    for(; k >=0&& temp < data[k]; k -=d)
                    {
                        data[k+d] =data[k];
                    }
                    data[k+d] =temp;
                }
            }
        }
        d = d/2;
    }
}