1 public static int rank(int[] array, int k) 2 { 3     int front = 0, rear = array.length - 1; 4        5     while(front <= rear)   //front = rear时, mid必与front和rear指向同一个元素 6     { 7         int mid = front + (rear - front) / 2; 8         if(k > array[mid]) front = mid + 1; 9         else if(k < array[mid]) rear = mid -1;10         else return mid;11     }12     return -1;13 }