排序_Shell_Sort(希尔排序)更正版

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

int N;

int a[1000];

void Shell_Sort ()//关于希尔排序的增量为奇数好还是为偶数好,上网查了查是奇数好,次数会少点,自己研究不出来为什么
//是奇数好,但是都这样说,自己就只能按照奇数的增量来分组了.
{
int d = (N >> 1) % 2 == 0? N >> 1 + 1 : N >> 1; //注意这里,一定要让增量变成是奇数
while (d > 0)
{
for (int i = d; i < N; i++)
{
int  j = i - d;
int t = a[i];
while (j >= 0 && t < a[j])
{
a[j + d] = a[j];
j -= d;
}
a[j + d] = t;
}
for (int i = 0; i < N; i++)
{
cout << a[i] << " ";
}
cout << endl;

if (d == 1) break; //这个是非常重要的...晕,前面写错了...也没有检查出来,因为要估计到奇数就会少算很多次数,就得加这一句话.要不然是死循环的;
d = (d >> 1) % 2 == 0 ? d >> 1 + 1 : d >> 1; //也要注意这里 也要保证增量是奇数.
}
}

int main()
{
cout << "Input the number that you want be sorted : " << endl;
cin >> N;
cout << "Please input the numbers:  " << endl;
for (int i = 0; i < N; i++)
{
cin >> a[i];
}
Shell_Sort ();
for (int i = 0; i < N; i++)
{
cout << a[i] << " ";
}
cout << endl;
system ("pause");
return 0;
}