shell排序是对直接插入方法的改进方法.
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/*-------------------------------------------------------------------------------------
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Shell_sort.h
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shell排序是对直接插入方法的改进,它并不是对相邻元素进行比较,而是对一定间隔的元素比较.
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选择增量序列的几种方法:(为方便,本例采用第一种增量序列)
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1. h[1]=size, h[k] = h[k-1]/2.
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最坏运行时间为O(N^2).
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最坏情形:数组长度为2^n,数组的偶数位置上同是一个数,奇数位置上也同是一个数,
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且比偶数位置的小。此时到最后一次遍历前shell排序实际上什么也没做。
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最后一次遍历相当于直接插入方法。
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2. Hibbard增量序列: h = 1,3,7,
,2^k-1![](http://www.cppblog.com/Images/dot.gif)
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这个的区别于上的主要的特点是相邻增量没有公因子
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最坏运行时间为O(n^{1.5});
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3. Sedgewick增量序列:{1,5,19,41,109,
}
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-------------------------------------------------------------------------------------*/
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#ifndef SHELL_SORT_H
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#define SHELL_SORT_H
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#include "typedef.h"
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void Shell_sort(T* a, int n)
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{
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for(int gap = n; gap > 0; gap = gap/2)
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{
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for(int i = 0; i != n; ++i)
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{
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T temp = a[i];
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int j = i - gap;
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for( ; j >= 0 && a[j] > temp; j = j-gap)
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a[j+gap] = a[j];
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a[j+gap] = temp;
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}
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}
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}
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#endif
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