How to sort a LinkedHashMap by value without Collections.sort()?

Question

I'm trying to write a selection sort method for a LinkedHashMap/ArrayList but I'm having issues and I'm not sure what's wrong. It compiles but doesn't actually sort the list. I'm trying to sort in descending order by value. Any help would be appreciated.

public static List sort(LinkedHashMap<String, Integer> words) {


        List<Map.Entry<String, Integer>> entries = new ArrayList<>(words.size());
        entries.addAll(words.entrySet());

        int max;

        for(int i = 0; i < entries.size(); i++) {

            max = entries.get(i).getValue();

            for(int j = i + 1; j < entries.size(); j++) {

                if (entries.get(j).getValue().compareTo(entries.get(max).getValue()) > 0) {

                    max = entries.get(j).getValue();
                }

            }

            if(max != i) {

                Map.Entry temp1 = entries.get(i);

                entries.set(entries.get(i).getValue(), entries.get(max));

                entries.set(entries.get(max).getValue(), temp1);
            }

        }

        return entries;
    }

It seems that throughout this code, indices and values are used interchangeably, max is assigned to values but then compared to an index. — khachik
– khachik, Commented Sep 13, 2018 at 1:53

RaffleBuffle · Accepted Answer · 2018-09-13 03:41:27Z

3

You're code is essentially correct, you've just mixed up values and indices in a few places.

You need to replace:

max = entries.get(i).getValue();

with

max = i;

This

max = entries.get(j).getValue();

with

max = j;

And

entries.set(entries.get(i).getValue(), entries.get(max));
entries.set(entries.get(max).getValue(), temp1);

with

entries.set(i, entries.get(max));
entries.set(max, temp1);

Make you sure you understand why the changes work.

edited Sep 13, 2018 at 3:41

answered Sep 13, 2018 at 2:44

RaffleBuffle

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2 Comments

Taylor Swift Over a year ago

I'm not sure if that's all that is wrong. It puts the highest value one first, as it should, but the rest are still scrambled.

RaffleBuffle Over a year ago

Yep, missed one. I've added it now.

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