14.插入排序--希尔排序(缩小增量排序)

希尔排序法基本思想：

把记录按下标的一定增量分组，对每组使用直接插入排序算法排序；

随着增量逐渐减少，每组包含的关键词越来越多，当增量减至1时，整个记录恰被分成一组，算法便终止

import java.util.Arrays;

/**
 * 希尔排序
 */
public class ShellSort {
    //交换式
    public static int[] shellSort(int[] arr){
        int length = arr.length;
        int temp = 0;
        int count = 0;
        //gap 为步长,也是组数
        for (int gap = length/2; gap >0 ; gap/=2) {
            //从第一组的第一个开始遍历所有元素。因为内部循环会-gap，也就是从第一组的第一个开始
            for (int i = gap; i <length; i++) {
                //遍历组中所有的元素，步长gap，会从后到前把大的排后面
                for (int j = i-gap; j >=0; j-=gap) {
                    if (arr[j]>arr[j+gap]){
                        temp = arr[j];
                        arr[j] = arr[j+gap];
                        arr[j+gap] = temp;
                    }
                }
                System.out.println(Arrays.toString(arr));
            }
            System.out.println("第"+(++count)+"轮，步长为"+gap+":="+Arrays.toString(arr));
        }
        return arr;
    }
    //交换式优化->位移式
    public static int[] shellSort2(int[] arr){
        int length = arr.length;
        int temp = 0;
        int count = 0;
        //gap 为步长,也是组数
        for (int gap = length/2; gap >0 ; gap/=2) {
            //
            for (int i = gap; i <length; i++) {
                int j = i;
                temp = arr[j];
                if (arr[j]<arr[j-gap]){
                    //把比temp的都向后移动
                    while (j-gap>=0&&temp<arr[j-gap]){
                        arr[j]=arr[j-gap];
                        j-=gap;
                    }
                    //temp插入
                    arr[j] = temp;
                }
                System.out.println(Arrays.toString(arr));
            }
            System.out.println("第"+(++count)+"轮，步长为"+gap+":="+Arrays.toString(arr));
        }
        return arr;
    }
    public static void main(String[] args){
        shellSort(new int[]{8,1,7,2,3,5,4,6,0});
        //[3, 1, 7, 2, 8, 5, 4, 6, 0]
        //[3, 1, 7, 2, 8, 5, 4, 6, 0]
        //[3, 1, 4, 2, 8, 5, 7, 6, 0]
        //[3, 1, 4, 2, 8, 5, 7, 6, 0]
        //[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //第1轮，步长为4:=[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //第2轮，步长为2:=[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 6, 7, 8]
        //[0, 1, 2, 3, 4, 5, 6, 7, 8]
        //第3轮，步长为1:=[0, 1, 2, 3, 4, 5, 6, 7, 8]
        shellSort2(new int[]{8,1,7,2,3,5,4,6,0});
        //[3, 1, 7, 2, 8, 5, 4, 6, 0]
        //[3, 1, 7, 2, 8, 5, 4, 6, 0]
        //[3, 1, 4, 2, 8, 5, 7, 6, 0]
        //[3, 1, 4, 2, 8, 5, 7, 6, 0]
        //[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //第1轮，步长为4:=[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //[0, 1, 4, 2, 3, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //第2轮，步长为2:=[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 3, 2, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 7, 6, 8]
        //[0, 1, 2, 3, 4, 5, 6, 7, 8]
        //[0, 1, 2, 3, 4, 5, 6, 7, 8]
        //第3轮，步长为1:=[0, 1, 2, 3, 4, 5, 6, 7, 8]
    }
}