Choose random object from array not the same as the randomly chosen object before

Logically, I want to pick a random value from an array repeatedly but i do not want to pick the same one as before. In my actual game i am creating a hole for the ball to roll through but i do not want the hole to have the same position as then the ball will just fall strait through my game, without having to move to get to the hole, activating the spawning of another value through onCollisionExit.

Below is my code if you find it necessary -

     using UnityEngine;
     using System.Collections;
     
     public class LevelSpawner : MonoBehaviour {
         public float height;
         public GameObject floor1;
     public GameObject floor2;
     public GameObject floor3;
     public GameObject floor4;
     public GameObject floor5;
     public GameObject floor6;
     public GameObject floor7;
     public GameObject floor8;
     public GameObject floor9;
     public GameObject edge;
     public GameObject edge2;
     int index;
 
     GameObject[] floors;
 
     // Use this for initialization
     void Start () {
         floors = new GameObject [9] { floor1, floor2, floor3, floor4, floor5, floor6, floor7, floor8, floor9 };
         Spawn();
     }
 
     public void Spawn ()
     {
         index = Random.Range(0,9);
         height = height - 24;
         GameObject floor;
         floor = Instantiate(floors[index] , new Vector3(0, height), floors[index].transform.rotation) as GameObject;
         Instantiate(edge, new Vector3(0, height + 36), Quaternion.identity);
         edge2.transform.position = new Vector3(edge.transform.position.x, height + 96, edge2.transform.position.z); 
     }
 
 }

The important bit is the first 4 lines of Spawn(), which is called from an another script.

I know there is the long way to do this by creating several other arrays for when the index is a certain value but not the one you just picked but that seems clunky and inefficient. I am aware of lists having watched the tutorial on them once but that is all and i am not comfortable with them.

Thanks,