每天一个小算法（Shell Sort2）

希尔排序：

伪代码：

input: an array a of length n with array elements numbered 0 to n − 1
inc ← round(n/2)
while inc > 0 do:
    for i = inc .. n − 1 do:
        temp ← a[i]
        j ← i
        while j ≥ inc and a[j − inc] > temp do:
            a[j] ← a[j − inc]
            j ← j − inc
        a[j] ← temp
    inc ← round(inc / 2)

C语言实现：

#include <stdio.h>
#include <stdlib.h>
#define LEN 10

int main()
{
     int i, j, temp;
     int gap = 0;
     int a[] = {10,9,8,7,6,5,4,3,2,1};
     while (gap<=LEN)
     {
          gap = gap * 3 + 1;
     }
     while (gap > 0)
     {
         for ( i = gap; i < LEN; 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;
     }
	 for(i=0;i<LEN;i++)
	 {
		 printf("%d\n",a[i]);
	 }
 }