什么是希尔排序？

#include <stdio.h>
#include <windows.h>
#include <stdint.h>
void Hill_sort(int a[],int size);
int main()
{
    int k;
    int num[9]={9,8,7,4,6,5,1,2,3}; 
    int sortsize=sizeof(num)/sizeof(num[0]);
    Hill_sort(num,sortsize);
    for(k=0;k<sortsize;k++)
    printf("%d\n",num[k]);
    system("pause");
    return 0;
}
void Hill_sort(int a[],int size)
{
    int i,j,k;
    int d;
    int temporary;
    for(d=size/2;d>=1;d=d/2)
    {
      printf("\nd=%d:",d);
      for(k=0;k<d;k++)
        for(i=k;i<size;i+=d)
        {
              printf("\ni=%d:",i);
            temporary=a[i];
            for(j=i-d;a[j]>temporary&&j>=0;j=j-d)
            {
                a[j+d]=a[j];
                printf("j=%d;",j);
            }
            a[j+d]=temporary;
         
        }
    }
}

void shell_Sort(ElemType A[],int n)
{
  int i, j, dk;
  for (int dk = n / 2; dk >= 1; dk--)
    for(int i=dk+1;i<=n;i++)
      if (A[i] < A[i - dk])
      {
        A[0] = A[i];
      }
  for (int j = i - dk; j > 0 && A[0] < A[j]; j -= dk)
    A[j + dk] = A[j];
  A[j + dk] = A[0];
}