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];
     }