java 实现归并排序

代码如下：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class MergSort {
    public final static int N = (int) (1e6 + 10);
   // public static int[] tem = new int[N];
    static int[] temp = new int[N];
    public static void main(String[] args) throws IOException {
//        int[] arr = {2,4,3,5,7,6};
//        int n = arr.length-1;
        //以控制台进行输入
        InputStreamReader in = new  InputStreamReader(System.in);//控制台进行输入
        //进行输入但这里一般是来年再一起写  BufferedReader bu  = new BufferedReader(new InputStreamReader(systen.in));
        BufferedReader bu  = new BufferedReader(in);
        String st  = bu.readLine();//数据的读取
        String ar[] = st.split(" ");//将字符串转化成字符串数组
        int num01= st.length();
        int[] arr = new int[num01];
        for ( int i = 0; i < num01 ; i++){
            arr[i] = Integer.parseInt((String.valueOf(st.charAt(i))));
        }



        Merg_Sort(arr, 0, arr.length-1);
        for (int i = 0; i < arr.length;i++){
            System.out.print(arr[i]+" ");
        }
    }

    private static void Merg_Sort(int[] arr, int l, int r) {
        if(l >= r) return ;
        //1.找到中间位置的数作基数
        int mid = r+l >> 1;
        //2.进行排序---左边的
        Merg_Sort(arr, l, mid);
        //2.进行排序---右边的
        Merg_Sort(arr, mid+1, r);
        //3.进行归并
        int k = 0;//进行记录我们新数组里的数据个数,新数组----temp数组
        int i = l;//左半边起点的指针
        int j = mid+1;//右边起点的指针
        while (i <= mid && j <=  r){
            if(arr[i] <= arr[j]) {
                temp[k++]=arr[i++];
            }else{
                temp[k++] = arr[j++];
            }

        }
        //进行判断，如果左半边没有循环完，则加到temp数组后面
        while (i <= mid) temp[k++] = arr[i++];
        //相应的如果有半边没有循环完，则加到temp 数组后面
        while (j <= r) temp[k++] = arr[j++];
        //最后进行复制
        for ( i = l, j = 0; i <= r; i++,j++){
                arr[i] = temp[j];
        }

    }

}