Binary Search(Java)(递归)

 public static int rank(int[] array, int k, int front, int rear)
 {
     if(front > rear)
         return -1;

     int mid = front + (rear - front) / 2;
     if(k == array[mid])
         return mid;
     else if(k > array[mid])
         return rank(array, k, mid + 1, rear);
     else
         return rank(array, k, front, mid - 1);
 }