Sorting Js Array according to pre-defined array of indexes

Question

hope you can help me fix this.

So I have one array with nested arrays:

mainArr: [[Carl, 20, Male],[Mike, 30, Male], [Chloe, 45, Female], ...]

Now this array needs to be sorted along another array containing a set order of indexes from the array above.

indexArr: [2,1,3,...]

Result here being:

sortedArr: [[Mike, 30, Male], [Carl, 20, Male], [Chloe, 45, Female], ...]

I thought about writing a ForEach loop with the second array, something along the lines of:

indexArr.forEach(i){
 sortedArr.push(mainArr[indexArr[i]]);
};

But I'm trying to avoid using loops with this function to keep it fast. I couldn't find anything relevant to my problem in any array documentation. Do you know a way to fill sortedArr or sort mainArr efficiently?

You can't do this without iterating over the entries in the array (whether that's an explicit for/foreach loop or an implicit loop such as map). — jarmod
– jarmod, Commented Oct 22, 2021 at 19:26

Anshu Jain · Accepted Answer · 2021-10-22 19:19:42Z

4

    indexArr.map(ind => mainArr[ind - 1])

answered Oct 22, 2021 at 19:19

Anshu Jain

2391 silver badge3 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Simon Veerman Over a year ago

Perfect, should've thought of that! Thanks alot

danh Over a year ago

good answer using a loop, which is necessary

Hudson Tavares Over a year ago

Each read with the array of positions, e.g. const item = mainArr[sortArr[index]] will have a constant number of steps (O(1) complexity). Still, you will need to go through the entire array for picking up all the items, an action whose number of steps increases as you have more items (O(n) complexity, which is what you're attempting to void). In this sense, I see no way out of looping to obtain all the items you need, regardless of the array method you use (e.g., this map will not avoid looping through the items), with no complexity difference - push or this approach will be O(1).

Simon Veerman Over a year ago

I've realized you're right, there's no way escaping the loop in this. It'll have to do!

Collectives™ on Stack Overflow

Sorting Js Array according to pre-defined array of indexes

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related