Merge Sort(Java)

　　 public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        int n = input.nextInt();
        int[] a = new int[n];
        
        for(int i = 0; i < a.length; i++)
            a[i] = input.nextInt();
        divide(a, 0, a.length - 1);
        
        for(int i = 0; i < a.length; i++)
            System.out.print(a[i] + " ");
    }
    
    public static void divide(int[] a, int front, int rear)
    {
        if(front == rear)
            return;
        
        int mid = front + (rear - front) / 2;
        divide(a, mid + 1, rear);  //分割右半边
        divide(a, front, mid);   //分割左半边
        merge(a, front, mid, rear);   //进行归并
    }
    
    public static void merge(int[] a, int front, int mid, int rear)
    {
        //先依次将排好序的元素放入b数组中(在放入b数组的过程中进行排序) 再将b数组元素依次放到a数组中
        int[] b = new int[rear - front + 1];
        int k = 0, i = front, j = mid + 1;
        
        while(i <= mid && j <= rear)
        {
            if(a[i] > a[j])
                b[k++] = a[j++];
            else
                b[k++] = a[i++];
        }
        if(i > mid)
            while(j <= rear)
                b[k++] = a[j++];
        else
            while(i <= mid)
                b[k++] = a[i++];
        
        for(int p = front, q = 0; p <= rear; p++, q++)
            a[p] = b[q];
    }