Module 4Sets: HashSet & BTreeSetLesson 11 of 2318 min

BTreeSet Ordered Uniques

Sorted unique keys; first/last; range queries mindset.

BTreeSet

rust

use std::collections::BTreeSet;

fn main() {
    let mut s = BTreeSet::new();
    s.insert(5);
    s.insert(1);
    s.insert(3);
    print!("sorted:");
    for x in &s {
        print!(" {x}");
    }
    println!();
    println!("min={:?} max={:?}", s.iter().next(), s.iter().next_back());
}

Output

sorted: 1 3 5
min=Some(1) max=Some(5)

first / last

rust

s.iter().next();      // min
s.iter().next_back(); // max

When to pick BTreeSet vs HashSet

Need	Use

------	-----

Fast membership only	HashSet

Sorted order / min-max	BTreeSet

Order stats lite	BTreeSet

Challenge

Given a stream of ints, print median of uniques so far using two structures or BTreeSet (hard mode: just print min/max gap).

Tips

Sorted iteration
next_back for max
Log n ops

Try it live

BTreeSet Ordered UniquesRust 2021

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Output

Press Run to compile and execute.