Total size of HashMap flatten elements

Language Design
1

Hello, is there a hashMapOf<String, MutableList<String>>() method returns total size of all elements in O(1)? Guys there just like me still make it old style forEach way.

2

There is nothing really “old” in using forEach() or loops. But if you are looking for functional way of doing this then:

z.values.sumOf { it.size }

If you’re looking for something similar to SO question, so create Map<String, Int> as a result then:

z.mapValues { it.value.size }

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3

Hm, even if it’s not O(1), at least it’s a 1-string method. Is there a case this method is used often or it’s hard to implement this variable?

4

I don’t think it is possible to do it in O(1). This data structure is basically a collection of collections, so we really need to iterate and count items. You can always create your own data structure that counts elements while adding them.

Sorry, I don’t understand the last sentence in your post.

5

I meant - can a new variable be implemented in a base map class - if it contains iterables, increase the total size of the map counting all its elements?

6

You can create your own data structure that implements MutableMap<String, MutableList<String>> and does this.

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