希尔排序

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#include<iostream>
using namespace std;

template<typename T>
void shellSort(T arr[], int n){

    int h = 1;
    while( h < n/3 )
        h = 3 * h + 1;
    // 计算 increment sequence: 1, 4, 13, 40, 121, 364, 1093...

    while( h >= 1 ){

        // h-sort the array
        for( int i = h ; i < n ; i ++ ){

            // 对 arr[i], arr[i-h], arr[i-2*h], arr[i-3*h]... 使用插入排序
            T e = arr[i];
            int j;
            for( j = i ; j >= h && e < arr[j-h] ; j -= h )
                arr[j] = arr[j-h];
            arr[j] = e;
        }

        h /= 3;
    }
}
int main()
{
    int arr[] = { 6, 4, 2, 8, 1, 3, 9, 5, 4, 7 };;
    shellSort(arr, 10);
    for (int i = 0; i < 10; i++)
        cout << arr[i];
}