希尔排序

希尔排序，也称递减增量排序算法，是插入排序的一种高速而稳定的改进版本。

C语言：

#include <stdio.h>
 
int main()
{
     const int n = 5;
     int i, j, temp; 
     int gap = 0;
     int a[] = {5, 4, 3, 2, 1}; 
     while (gap<=n)
     {
          gap = gap * 3 + 1;
     } 
     while (gap > 0) 
     {
         for ( i = gap; i < n; i++ )
         {
             j = i - gap;
             temp = a[i];             
             while (( j >= 0 ) && ( a[j] > temp ))
             {
                 a[j + gap] = a[j];
                 j = j - gap;
             }
             a[j + gap] = temp;
         }
         gap = ( gap - 1 ) / 3;
     }    
 }

C++：

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;
         }
}

JAVA：

static <E extends Comparable<? super E>> void shellSort(List<E> a) {
    int h = 1;
    while (h < a.size()/3) h = h*3 + 1;    // <O(n^(3/2)) by Knuth,1973>: 1, 4, 13, 40, 121, ...
    for (; h >= 1; h /= 3)
        for (int i = h; i < a.size(); i++)
            for (int j = i; j >= h && a.get(j).compareTo(a.get(j-h)) < 0; j-=h)
                Collections.swap(a, j, j-h);
}