MergeSort

class Merge{    private static int[] aux;//定义一个数组用于存储归并时存储原数组    public static void sort(int[] a)    {        aux = new int[a.length];//将数组aux的长度定义为与原数组的长度是一样的        sort(a ,0, a.length-1);//将原数组进行划分    }    public static void sort(int[] a,int low,int high)    {        if (high<=low)//如果子数组中长度为1，此时就不再进行sort了        {            return;        }        int mid =low+ (high-low)/2;//定义一个中位数        sort(a ,low,mid);//将a数组中的元素的前一半尽心再次sort        sort(a ,mid+1,high);//将数组的后一半进行sort        merge(a,low,mid,high);//将数组的前一半和后一半进行一个merge    }    public static void merge(int[] a,int low,int mid,int high)    {        int leftIndex = low;//定义前一半数组元素的Index        int rightIndex = mid+1;//定义后一半元素的Index        int tempIndex =low;//定义当前子数组的起始位置元素的Index        for (int i =low;i<=high ;i++ )//将元素组a的元素复制到数组啊aux中        {            aux[i] = a[i];        }        while ((leftIndex<=mid)&&(rightIndex<=high))//实现归并        {            if (aux[leftIndex]<aux[rightIndex])            {                a[tempIndex] = aux[leftIndex];                leftIndex++;            }            else             {                a[tempIndex] = aux[rightIndex];                rightIndex++;            }            tempIndex++;        }        if (leftIndex>mid)        {            for (;rightIndex<=high;rightIndex++,tempIndex++)            {                a[tempIndex] = aux[rightIndex];            }        }        else        {            for (;leftIndex<=mid;leftIndex++,tempIndex++ )            {                a[tempIndex] = aux[leftIndex];            }        }    }    public static void printArr(int[] a)//输出数组    {        for (int i=0;i<a.length ;i++ )        {            if (i==0)            {                System.out.print("{"+a[i]+",");            }            else if (i<a.length-1)            {                System.out.print(a[i]+",");            }            else                 System.out.println(a[i]+"}");        }    }}class MergeSort{    public static void main(String[] args)    {        int[] a = new int[]{3,44,38,5,47,15,36,26,27,2,46,4,19,50,48};        int[] aux = new int[a.length];        Merge.sort(a);        Merge.printArr(a);    }}