sort a multi-dimensionnal table

jimlev · August 2014

Hi !
Before I launch myself in an too-big-for-me bunch of code, it would be nice if someone can confirm I'm on the right way.

Here it is :
I have a multi-dim table like that one :
-- name of the player / score / energy / does he have a bonus?
playerRanking = {{"john", 12, 0, false},{"charles", 17, 5, false},{"tony", 3, 3, true},{"marcello", 17, 11, false},{"rebecca", 12, 0, true}}

my goal is to sort that table by the players score. In case of equality, the energy parameter should be used to decide. And then, if players have or not a bonus.

the result should look like :
playerRanking = {{"marcello", 17, 11, false},{"charles", 17, 5, false},{"rebecca", 12, 0, true},{"john", 12, 0, false},{"tony", 3, 3, true}}

The way I'm going to approach the problem is :
1. copy all the score values in a simple table and sort it with the table.sort method.
2. with a loop, check in my playerRanking table if there is equality on the highest score
3. if answer is no, I copy that player to a temp table at the first index
4. if yes, I compare the other parameters to decide. And then, I copy these players at the first and second indexes
5. etc. on the next values from my sorted list

Am I on the right way. Is there a more trivial method to do that ?

thx !

boriskey · August 2014

hi, check these posts

http://stackoverflow.com/questions/2038418/associatively-sorting-a-table-by-value-in-lua

http://stackoverflow.com/questions/15706270/sort-a-table-in-lua

http://lua.gts-stolberg.de/en/table.php#table.sort_(table_[,_comp])

hope it helps

OZApps · August 2014

@jimlev,
table.sort is a very powerful function and you would get what you want even with a multi-dimension table. To do a custom sort, you can write your own function or a simple comparison statement like a > b, for mutli-dimension sort, you can use a[1] > b[1] or the element that you want to sort on.

Hope that helps your problem.

ar2rsawseen · August 2014

Something like this should work:

table.sort(t, function(a,b)
    if a[2] == b[2] then
        if a[3] == b[3] then
            return a[4]
        end
        return tonumber(a[3]) > tonumber(b[3])
    end
    return tonumber(a[2]) > tonumber(b[2])
end)

jimlev · August 2014

real thx to all !
I 'm not familiar of the possibilities of giving a function in a method's parameters. So, I gonna give a try to the ar2rsawseen solution and, if it works (what I can't doubt) I hope that applying it will help me understand it

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