Algorithm used to prevent a player from getting their same card - sorting

Question

I have a game I am coding in Tabletop Simulator where all players (P) is given a card (C). Once memorized all players put the card back into the deck (D), shuffled, and then all players are dealt one of the cards from the same deck (D). I am trying to code the simplest algorithm that prevents a player from getting their own card. Now when it comes to coding this should be simple I assume instead of creating simulations to run until it is successful.

Answer 1

Say you have the following:
deck, a randomized deck containing all the cards (including those the players have seen).
seen_card_id_by_player, a lookup table that give you the guid of the card a player has seen.
Then the solution is simply
local card_ids = {}
for i, card_data in ipairs(deck.getObjects()) do
table.insert(card_ids, card_data.guid)
end
for player, seen_card_id in pairs(seen_card_id_by_player) do
local card_id = table.remove(card_ids)
if card_id == seen_card_id then
local i = math.random(1, #card_ids)
card_ids[i], card_id = card_id, card_ids[i]
end
-- Deal the specific card.
deck.takeObject({
guid = card_ids[i],
position = player.getHandTransform().position,
flip = true,
})
end
When we pick the card the player has already seen, it is placed back at a random location among the remaining cards. This ensures that every card has an equal chance of being drawn by the next player. This is the underlying principle of the Fisher-Yates shuffle.
Full demonstration
function broadcast_error(msg)
broadcastToAll(msg, { r=1, g=0, b=0 })
end
function get_cards_seen_by_players()
local player_ids = Player.getAvailableColors()
local error = false
local seen_card_by_player = {}
for i, player_id in ipairs(player_ids) do
local player = Player[player_id]
local hand_objs = player.getHandObjects()
local player_error = false
if #hand_objs > 1 then
player_error = true
elseif #hand_objs == 1 then
local card = hand_objs[1]
if card.tag ~= "Card" then
player_error = true
else
seen_card_by_player[player] = card
end
end
if player_error then
broadcast_error(player_id .. " doesn't have a valid hand.")
error = true
end
end
if error then
return nil
end
return seen_card_by_player
end
function run()
local deck = getObjectFromGUID("...")
local seen_card_by_player = get_cards_seen_by_players()
if seen_card_by_player == nil or next(seen_card_by_player) == nil then
return
end
local seen_card_id_by_player = {}
for player, card in pairs(seen_card_by_player) do
local card_id = card.guid
seen_card_id_by_player[player] = card_id
card.putObject(deck)
end
deck.randomize()
local card_ids = {}
for i, card_data in ipairs(deck.getObjects()) do
table.insert(card_ids, card_data.guid)
end
for player, seen_card_id in pairs(seen_card_id_by_player) do
local card_id = table.remove(card_ids)
if card_id == seen_card_id then
local i = math.random(1, #card_ids)
card_ids[i], card_id = card_id, card_ids[i]
end
deck.takeObject({
guid = card_ids[i],
position = player.getHandTransform().position,
flip = true,
})
end
end
Create a game with a deck of cards. Place the above code in Global, replacing ... with the deck's GUID. To run the demonstration, deal one card to any number of players, then use /execute Global.call("run") in the chat window.