从 Random.Range 中排除值

Question

I am trying to make a card game. In this game, there are only two of each card. So the goal is that whenever a certain card is drawn two times, that card cannot be drawn anymore. Currently, there are 3 different cards. I made a random range between 0 and 3. So what im trying to achieve is that if lets say the number 1 gets picked 2 times, then if it picks 1 again that it skips that round and picks another number until that number is not any number that is picked 2 times.

public GameObject[] cards;

public Transform spawnPos;

Vector3 tempPos;

int randomNum;

int C2i = 2;
int C3i = 2;
int C4i = 2;

bool C2 = true;
bool C3 = true;
bool C4 = true;

void Update()
{
    if(Input.GetMouseButtonDown(0))
    {
        SpawnCard();
    }

    if (C2i <= 0)
    {
        C2 = false;
    }

    if (C3i <= 0)
    {
        C3 = false;
    }

    if (C4i <= 0)
    {
        C4 = false;
    }
}

void SpawnCard()
{
    randomNum = Random.Range(0, cards.Length);

    CheckCards();

    if (C2 == true)
    {
        Instantiate(cards[randomNum], spawnPos.position, spawnPos.rotation);
    }
    else
    {
        SpawnCard();
    }

    if (C3 == true)
    {
        Instantiate(cards[randomNum], spawnPos.position, spawnPos.rotation);
    }
    else
    {
        SpawnCard();
    }

    if (C4 == true)
    {
        Instantiate(cards[randomNum], spawnPos.position, spawnPos.rotation);
    }
    else
    {
        SpawnCard();
    }

    tempPos = spawnPos.position;

    tempPos.x += 1.5f;

    spawnPos.position = tempPos;
}

void CheckCards()
{
    if (randomNum == 0)
    {
        C2i -= 1;
    }

    if (randomNum == 1)
    {
        C3i -= 1;
    }

    if (randomNum == 2)
    {
        C4i -= 1;
    }
}

Answer 1

You could rather generate your deck once basically how it works in real life. This is way better to maintain and also easier to understand.

1. Store your cards deck in a separate collection so you can easily restart with a new deck without loosing your original setup.

2. Simply add two of each card prefab to the deck and remove them whenever you draw a card.

3. Either shuffle the entire deck so you can simply draw the cards in order later (eg also multiple at a time) or use a random index of each card you draw.

Something like

using System.Linq;

...

// 1. You leave this collection untouched
// You only use it to create your deck from these prefabs
public GameObject[] cards;
public Transform spawnPos;

// NOT NEEDED
//private Vector3 tempPos;
//int randomNum;
//int C2i = 2;
//int C3i = 2;
//int C4i = 2;
//bool C2 = true;
//bool C3 = true;
//bool C4 = true;

// 1. Store your runtime deck here
// This will be generated and used to draw cards later
private readonly List<GameObject> deck = new List<GameObject>();

private void Awake ()
{
    CreateNewDeck();
}

private void CreateNewDeck()
{
    // 1. Start with an empty deck
    deck.Clear();

    // 2. Add two of each card prefabs
    foreach(var card in cards)
    {
        deck.Add(card);
        deck.Add(card);
    }

    // 3. Either shuffle the deck
    // If you use this then later you don't need random indices
    // the deck itself already is random so you can just draw them one by one later
    deck = deck.OrderBy(c => Random.value).ToList();
}

void Update()
{
    if(Input.GetMouseButtonDown(0))
    {
        SpawnCard();
    }
}

private void SpawnCard()
{
    if(deck.Count == 0) 
    {
        Debug.LogError("Deck is empty!", this);
        return;
    }

    // 3. If you did shuffle you can simply use 0
    var index = 0;
    // If you did not shuffle in Awake then pick random index from deck
    //var index = Random.Range(0, deck.Count); 
    // Pick card by index
    var card = deck[index];
    // Remove from deck
    deck.RemoveAt(index);   
    // Spawn card
    Instantiate(card, spawnPos.position, spawnPos.rotation);

    spawnPos.position += Vector3.right * 1.5f;
}

Answer 2

List<(int Card, int NumRemaining)> availableCards = Enumerable.Range(0, cards.Length).Select(i => (i, 2)).ToList(); int PickCard() { if (availableCards.Count == 0) throw new Exception("No cards remaining"); var cardIndex = availableCards.Count == 1 ? 0 : Random.Range(0, availableCards.Count); var (card, numRemaining) = availableCards[cardIndex]; if (numRemaining > 1) { availableCards[cardIndex] = (card, numRemaining - 1); } else { availableCards.RemoveAt(cardIndex); } return card; }