排序6：归并排序（递归方式）

/**
 * @desc: 归并排序
 * @author: 毛会懂
 * @create: 2020-12-24 11:17:00
 **/
public class Merge {

    public static void sort(Comparable[] arr){
        int low = 0;
        int high = arr.length - 1;
        sort(arr,low,high);
    }

    public static void sort(Comparable[] arr,int low,int high){
        if(low >= high){
            return;
        }
        int middle = low + (high - low) / 2;

        sort(arr,low,middle);
        sort(arr,middle + 1,high);
        merge(arr,low,middle,high);
    }

    public static void merge(Comparable[] arr,int low,int middle,int high){
        //这种方式每次递归都要创建一个temp数组，也不太友好
        Comparable[] temp = new Comparable[high -low +1];

        //定义指向temp的下标位置
        int k = 0;
        //定义指向arr[low] -- arr[middle]的下标位置
        int i = low;
        //定义指向arr[middle + 1] -- arr[high]的下标位置
        int j = middle + 1;
        while (i <= middle && j <= high){
            if(isExchange(arr[i],arr[j])){
                temp[k++] = arr[j++];
            }else{
                temp[k++] = arr[i++];
            }
        }

        while (i <= middle){
            temp[k++] = arr[i++];
        }

        while (j <= high){
            temp[k++] = arr[j++];
        }

        //最后把temp数组赋值到arr数组中
        for(int index = low; index <=high;index++){
            arr[index] = temp[index - low];
        }
    }

    private static Boolean isExchange(Comparable o1,Comparable o2){
        return o1.compareTo(o2) > 0;
    }
}

    //归并排序
    public static void main(String[] args) {
//        Integer[] arr = {10,8,20,30,5,7,4,12,40,30,1,2,4,3,100,5,32,45,23,66,45,7,55,79,6};
//        Merge.sort(arr);
//        Arrays.asList(arr).forEach(System.out::println);

        Person[] persions = {new Person("b", 11), new Person("a", 10), new Person("c", 12), new Person("b", 111),
                new Person("a", 5), new Person("c", 4)};
        Merge.sort(persions);
        for (Person person : persions) {
            System.out.println(person);
        }
    }