壳排序

ShellSort主要是插入排序的一种变体。在插入排序中，我们仅将元素向前移动一个位置。当一个元素必须向前移动时，涉及许多移动。 shellSort的想法是允许交换远项。在shellSort中，我们对数组进行h排序以获得较大的h值。我们一直将h的值减小到1。如果每个第h个元素的所有子列表都被排序，则称数组为h排序。

以下是ShellSort的实现。

C++

// C++ implementation of Shell Sort
#include  
using namespace std;
  
/* function to sort arr using shellSort */
int shellSort(int arr[], int n)
{
    // Start with a big gap, then reduce the gap
    for (int gap = n/2; gap > 0; gap /= 2)
    {
        // Do a gapped insertion sort for this gap size.
        // The first gap elements a[0..gap-1] are already in gapped order
        // keep adding one more element until the entire array is
        // gap sorted 
        for (int i = gap; i < n; i += 1)
        {
            // add a[i] to the elements that have been gap sorted
            // save a[i] in temp and make a hole at position i
            int temp = arr[i];
  
            // shift earlier gap-sorted elements up until the correct 
            // location for a[i] is found
            int j;            
            for (j = i; j >= gap && arr[j - gap] > temp; j -= gap)
                arr[j] = arr[j - gap];
              
            //  put temp (the original a[i]) in its correct location
            arr[j] = temp;
        }
    }
    return 0;
}
  
void printArray(int arr[], int n)
{
    for (int i=0; i

---

Java

// Java implementation of ShellSort
class ShellSort
{
    /* An utility function to print array of size n*/
    static void printArray(int arr[])
    {
        int n = arr.length;
        for (int i=0; i 0; gap /= 2)
        {
            // Do a gapped insertion sort for this gap size.
            // The first gap elements a[0..gap-1] are already
            // in gapped order keep adding one more element
            // until the entire array is gap sorted
            for (int i = gap; i < n; i += 1)
            {
                // add a[i] to the elements that have been gap
                // sorted save a[i] in temp and make a hole at
                // position i
                int temp = arr[i];
  
                // shift earlier gap-sorted elements up until
                // the correct location for a[i] is found
                int j;
                for (j = i; j >= gap && arr[j - gap] > temp; j -= gap)
                    arr[j] = arr[j - gap];
  
                // put temp (the original a[i]) in its correct
                // location
                arr[j] = temp;
            }
        }
        return 0;
    }
  
    // Driver method
    public static void main(String args[])
    {
        int arr[] = {12, 34, 54, 2, 3};
        System.out.println("Array before sorting");
        printArray(arr);
  
        ShellSort ob = new ShellSort();
        ob.sort(arr);
  
        System.out.println("Array after sorting");
        printArray(arr);
    }
} 
/*This code is contributed by Rajat Mishra */

Python3

# Python3 program for implementation of Shell Sort
  
def shellSort(arr):
  
    # Start with a big gap, then reduce the gap
    n = len(arr)
    gap = n//2
  
    # Do a gapped insertion sort for this gap size.
    # The first gap elements a[0..gap-1] are already in gapped 
    # order keep adding one more element until the entire array
    # is gap sorted
    while gap > 0:
  
        for i in range(gap,n):
  
            # add a[i] to the elements that have been gap sorted
            # save a[i] in temp and make a hole at position i
            temp = arr[i]
  
            # shift earlier gap-sorted elements up until the correct
            # location for a[i] is found
            j = i
            while  j >= gap and arr[j-gap] >temp:
                arr[j] = arr[j-gap]
                j -= gap
  
            # put temp (the original a[i]) in its correct location
            arr[j] = temp
        gap //= 2
  
  
# Driver code to test above
arr = [ 12, 34, 54, 2, 3]
  
n = len(arr)
print ("Array before sorting:")
for i in range(n):
    print(arr[i]),
  
shellSort(arr)
  
print ("\nArray after sorting:")
for i in range(n):
    print(arr[i]),
  
# This code is contributed by Mohit Kumra

C#

// C# implementation of ShellSort
using System;
  
class ShellSort
{
    /* An utility function to 
       print array of size n*/
    static void printArray(int []arr)
    {
        int n = arr.Length;
        for (int i=0; i 0; gap /= 2)
        {
            // Do a gapped insertion sort for this gap size.
            // The first gap elements a[0..gap-1] are already
            // in gapped order keep adding one more element
            // until the entire array is gap sorted
            for (int i = gap; i < n; i += 1)
            {
                // add a[i] to the elements that have
                // been gap sorted save a[i] in temp and
                // make a hole at position i
                int temp = arr[i];
  
                // shift earlier gap-sorted elements up until
                // the correct location for a[i] is found
                int j;
                for (j = i; j >= gap && arr[j - gap] > temp; j -= gap)
                    arr[j] = arr[j - gap];
  
                // put temp (the original a[i]) 
                // in its correct location
                arr[j] = temp;
            }
        }
        return 0;
    }
  
    // Driver method
    public static void Main()
    {
        int []arr = {12, 34, 54, 2, 3};
        Console.Write("Array before sorting :\n");
        printArray(arr);
  
        ShellSort ob = new ShellSort();
        ob.sort(arr);
  
        Console.Write("Array after sorting :\n");
        printArray(arr);
    }
} 
  
// This code is contributed by nitin mittal.

输出：

Array before sorting:
12 34 54 2 3
Array after sorting:
2 3 12 34 54

时间复杂度：上述shellsort实现的时间复杂度为O(n ² )。在上面的实现中，每次迭代的差距减少了一半。还有许多其他方法可以减少时间间隔，从而导致更好的时间复杂度。有关更多详细信息，请参见此。

参考：
https://www.youtube.com/watch?v=pGhazjsFW28
http://en.wikipedia.org/wiki/Shellsort

快照：

壳排序测验

GeeksforGeeks / GeeksQuiz上的其他排序算法：

• 选择排序
• 气泡排序
• 插入排序
• 合并排序
• 堆排序
• 快速排序
• 基数排序
• 计数排序
• 桶分类

  排序的编码实践。