void shellsort(int *data, size_t size){    for (int gap = size / 2; gap > 0; gap /= 2)        for (int i = gap; i < size; ++i)        {              int key = data[i];             int j = 0;             for( j = i -gap; j >= 0 && data[j] > key; j -=gap)             {                data[j+gap] = data[j];              }               data[j+gap] = key;         }}

　　概念很简单，就是先跳着排，然后跳跃排序顺序逐渐变短