Checking if more than 2 values are equal

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#1

I am looking for a way to check if more than 2 values are equal.

The Premise

I have been attempting to remake The Coding Train’s Tic Tac Toe game (seen here) in Roblox, and to make the game on a 5x5 grid. The board is a table that holds 5 more
tables, each with 5 string values to determine blank, X or O.

The Problem

To check if every value in a row is equal (meaning someone has won the game), he uses a for loop and does something like:

board[i][1] == board[i][2] == board[i][3] == board[i][4] == board[i][5]

This does not appear to work in Lua, and I did some reading and it turns out that == returns true if the given values are equal. When x == y == z is used in Lua, (from my knowledge) x == y will return true or false, and then it will check if true or false is equal to z.

This is, obviously, not the desired outcome. I have poked around the Devforum for a while to see if anyone else had this problem, but I might have missed a post so let me know.

Current Code

Here’s my current function for checking for a winner:

local function checkWinner()
	local winner = nil
	
	-- horizontal checks
	for i = 1, #board do
		if board[i][1] == board[i][2] == board[i][3] == board[i][4] == board[i][5] then
			winner = board[i][1]
		end
	end
	
	-- vertical checks
	for i = 1, #board do
		if board[1][i] == board[2][i] == board[3][i] == board[4][i] == board[5][i] then
			winner = board[1][i]
		end
	end
	
	-- diagonal checks
	if board[1][1] == board[2][2] == board[3][3] == board[4][4] == board[5][5] then
		winner = board[1][1]
	end
	if board[1][5] == board[2][4] == board[3][3] == board[4][2] == board[5][1] then
		winner = board[1][5]
	end
	
	if (winner == nil) and (#available == 0) then
		print("It's a tie!")
	elseif winner ~= nil then
		print(winner .. " wins!")
	else
		print("No outcome yet!")
	end
end

Thanks in advance for any solutions!

#2 
if x == y and x == z and y == z
1 Like
#3

I should’ve mentioned that I’m avoiding this because the amount you have to type scales up very quickly with this method. I’ll probably resort to this in the tic-tac-toe game, but I’d also like to find something that works for large amounts of values.

#4

You can try something like this:

local t = {1, 1, 1, 1, 3, 3, 3, 3, 4, 5, 6, 7, 8, 11, 11, 11, 11} -- 1, 3, 11

local function DuplicatesExist(arr: {any}): {any}
	local curr = {}
	local hash = {}
	
	for _,v in ipairs(arr) do
		if not table.find(curr, v) then
			table.insert(curr, v)
		else
			if not table.find(hash, v) then
				table.insert(hash, v)
			end
		end
	end
	
	return hash
end

for i,v in ipairs(DuplicatesExist(t)) do
	warn(v) -- 1, 3, 11
end

if #DuplicatesExist(t) > 2 then
	warn("NOO THERE ARE MORE THAN 2 EQUAL VALUES!!") -- this prints out
end
#5

This may work, but I would have to restructure most of the current code I have. I’ll definitely keep this function saved for future use though.

1 Like
#6

You can use a for loop with #array (or #array - 1 if you don’t wanna check arr[1] again) iterations. You would just have to check if the element at arr[i] is equal to the first element, arr[1]. If it isn’t then continue to the next row. If the loop reached the #arrayth iteration, then the entire row matched. This should work for an array of any size.

Ex:

local board = {1, 1, 1, 1, 1, 1, 1}

local function checkWinner()
	local first = board[1]
	
	for row = 1, #board do
		if board[row] ~= first then
			print'Entire row didn\'t match :('
			break
		elseif row == #board then
			print'Entire row matched!'
		end
	end
end

checkWinner()

You can also check out my reply to someone who also needed help implementing tic tac toe here: Help with Tic-Tac-Toe game - #3 by heII_ish
I pretty much gave them the entire implementation for checking only the rows of the board (adding checks for columns and diagonals should be pretty straightforward from there)

#7

Thanks! This seems to be the most straightforward method, although I’ve already implemented an optimised version of what @Katrist posted. I may rewrite the system once it is completed.

#8 
local function isEqualSet(value, ...)
	return value == math.min(...) and value == math.max(...)
end

print(isEqualSet(1, 1, 2, 3, 4, 5, 6, 7, 8, 9)) --false
print(isEqualSet(1, 1, 1, 1, 1, 1, 1, 1, 1, 1)) --true

Use this if you need to check for equality across a large set of values.