how instantiate random enemy only once on random spawn

Questions & Answers
1

is it possible to spawn every enemy only once and use every spawn point only once?

here my code :

var spawnPoints : Transform[];  // Array of spawn points to be used.
var enemyPrefabs : GameObject[]; // Array of different Enemies that are used.
var amountEnemies = 16;  // Total number of enemies to spawn.

function newSpawn() { 

   for (i=0; i<amountEnemies; i++) // How many enemies to instantiate total.
   {
      var obj : GameObject = enemyPrefabs[Random.Range(0, enemyPrefabs.length-1)]; // Randomize the different enemies to instantiate.
      var pos: Transform = spawnPoints[Random.Range(0, spawnPoints.length-1)];  // Randomize the spawnPoints to instantiate enemy at next.
      Instantiate(obj, pos.position, pos.rotation); 
   } 
}
2

Easiest way to do this would be using a list instead of arrays. You'd use the same logic as in your script, but after spawning you'd remove the prefab and spawn point from the list, which is as easy as 

prefabList.(RemoveAt(index));