CODEWITHSUNDEEP
rust
terett
terett

Reputation: 447

How to convert BTreeSet to BTreeMap?

I have a BTreeSet object and I want to convert it into a BTreeMap with default indices (i.e., starting from 0 and incrementing). More precisely, given this:

let set = BTreeSet::from([0, 2, 4, 6, 8]);

I want to end up with BTreeMap<usize, usize> that holds [(0, 0), (1, 2), (2, 4), (3, 6), (4, 8)]. I can do it with a loop for example as

let mut tree = BTreeMap::new();
for (i, v) in set.clone().into_iter().enumerate() {
    tree.insert(i, v);
}

But is there any shortcut (i.e., one line code) that does the same?

Upvotes: 1

Views: 282

Answers (1)

Masklinn
Masklinn

Reputation: 42272

But is there any shortcut (i.e., one line code) that does the same?

let map = set.iter().copied().enumerate().collect::<BTreeMap<_, _>>();
println!("{:?}", map);

{0: 0, 1: 2, 2: 4, 3: 6, 4: 8}

tho note that this is a BTreeMap<usize, i32>, because i32 is the default resolution for {integer} literals if they're otherwise unconstrained, which is the case here.

Upvotes: 3

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