Java归并排序

package 排序;

import java.util.Arrays;

public class Merge_Sort {
    public void Merge_Sort(int[] array,int left,int right,int[] temp){
        //拆分
            if (left<right) {
                int mid=(left+right)/2;
                Merge_Sort(array,left,mid,temp);
                Merge_Sort(array,mid+1,right,temp);
                Merge(array,left,mid,right,temp);
            }
    }

    private void Merge(int[] array, int left, int mid, int right, int[] temp) {
        int i=left;//左边指针
        int j=mid+1;//右边指针
        int index=0;//temp数组指针
        while (i<=mid&&j<=right){
            if(array[i]<=array[j]){
                //左边更小，放进temp,指针同时移动
                temp[index++]=array[i++];
            }else {
                //右边更小，放进temp,指针同时移动
                temp[index++]=array[j++];
            }
        }
        //左边或者右边有一个已经放完了，另一个还没放完
        //左边剩余
        while (i<=mid){
            temp[index++]=array[i++];
        }
        //右边剩余
        while (j<=right){
            temp[index++]=array[j++];
        }
        //解释一下这里，有若干个Merge过程，每次的归并都写进temp里，然后修改对应的array,局部修改，局部有序，最后全局有序
        index=0;
       while (left<=right){
           array[left++]=temp[index++];
       }

    }
}

package 排序;

import java.util.Arrays;

public class Test {
    public static void main(String[] args) {
        int[] array=new int[]{4,3,2,1};
        int[] temp=new int[4];
        System.out.println(Arrays.toString(array));

        Merge_Sort merge_sort = new Merge_Sort();
        merge_sort.Merge_Sort(array,0, array.length-1,temp);
        System.out.println(Arrays.toString(array));

    }
}