算法：两种步长的希尔排序算法

算法：两种希尔排序算法

/**
 * 希尔排序
 * 不同步长的算法
 * @author mackxu
 *
 */
class ShellSort {
    private int[] a = {5,2,4,3,1};
    private int nElems = 5;
    
    public ShellSort() {
        
    }
    
    public void display() {
        for(int elem : a) {
            System.out.print(elem + " ");
        }
        System.out.println();
    }
    /**
     * 外循环确定步长大小
     * 中循环
     * 内循环
     */
    public void shell_sort() {
        int in, temp;
        for (int gap = nElems/2; gap>0; gap/=2) {
            for (int out=gap; out<nElems; out++) {            
                temp = a[out];        //待排的元素
                in = out;
                //while循环中的两个判断条件
                while(in>gap-1 && a[in-gap]>temp){
                    a[in] = a[in-gap];
                    in -= gap;
                }
                a[in] = temp;                
            }
        }
        
    }
    
    public void shell_sort2() {
        int out, in;
        int temp;
        
        //获取最大步长
        //可取值有4、13、40、121、364、1093....
        int gap = 1;
        while(gap<=nElems/3)
            gap = gap*3 + 1;
        while(gap>0) {
            for(out=gap; out<nElems; out++) {
                temp = a[out];            //待排的元素
                in = out;
                while(in>gap-1 && a[in-gap]>=temp) {
                    a[in] = a[in-gap];    //值大的后移, 腾出位置,等待填充
                    in -= gap;
                }
                a[in] = temp;            //找到合适的位置，填充进去
            }
            gap = (gap-1)/3;            //改变步长
        }
        
    }    
}