how to be sure that several don't instantiate in the same spot

Questions & Answers
1

so I’ve been having some trouble and I was wondering the way to make sure that they don’t spawn in the same spot public GameObject cardPlacement = new GameObject[7]; // Number of placements on the table
public GameObject cards; // The cards, that have to be placed randomly on the table

void Start()
{
	int randomPlace1 = Random.Range(0, cardPlacement.Length); 
	int randomPlace2 = Random.Range(0, cardPlacement.Length);
	int randomPlace3 = Random.Range(0, cardPlacement.Length);
	int randomPlace4 = Random.Range(0, cardPlacement.Length);
	int randomCard = Random.Range(0, cards.Length);        // Get Random Card
	
	// Instantiate random card into a random place on the table and position the card on that place
	Instantiate(cards[randomCard], cardPlacement[randomPlace1].transform.position, cardPlacement[randomPlace1].transform.rotation);
	
	Instantiate(cards[randomCard], cardPlacement[randomPlace2].transform.position, cardPlacement[randomPlace2].transform.rotation);
	
	Instantiate(cards[randomCard], cardPlacement[randomPlace3].transform.position, cardPlacement[randomPlace3].transform.rotation);
	
	Instantiate(cards[randomCard], cardPlacement[randomPlace4].transform.position, cardPlacement[randomPlace4].transform.rotation);
}
2

One way you can do this is to keep a list of indices that are still valid to be chosen and choose from that list instead of from the full range. Something like this:

//using System.Collections.Generic;

List<int> validIndices = new List<int>();
for (int i = 0; i < cardPlacement.Length; i++)
	validIndices.Add(i);
int randomPlace1 = validIndices[Random.Range(0, validIndices.Count)];
validIndices.Remove(randomPlace1);
int randomPlace2 = validIndices[Random.Range(0, validIndices.Count)];
validIndices.Remove(randomPlace2);
int randomPlace3 = validIndices[Random.Range(0, validIndices.Count)];
validIndices.Remove(randomPlace3);
int randomPlace4 = validIndices[Random.Range(0, validIndices.Count)];
int randomCard = Random.Range(0, cards.Length);

//Instantiate...