find the range of all keys in a map in rust

To find the range of all the keys in a HashMap in Rust, you can use the RangeBounds trait and the keys method of the HashMap.

Here's an example code snippet:

main.rs
use std::collections::HashMap;
use std::ops::RangeBounds;

fn main() {
    let mut map = HashMap::new();
    map.insert("k1", "v1");
    map.insert("k2", "v2");
    map.insert("k3", "v3");
    map.insert("k4", "v4");

    let key_range = map.keys().fold((usize::MAX, usize::MIN), |acc, k| {
        let start = if k.start_bound().is_inclusive() {
            k.start().len()
        } else {
            k.start().len() + 1
        };
        let end = if k.end_bound().is_inclusive() {
            k.end().len()
        } else {
            k.end().len() - 1
        };
        (acc.0.min(start), acc.1.max(end))
    });

    println!("Key range: {:?}-{:?}", key_range.0, key_range.1);
}
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Here, we create a new HashMap and insert some key-value pairs into it. We then use the keys method to get an iterator over all the keys in the map.

We use fold to iterate over each key and update the minimum and maximum key lengths seen so far. We do this by checking the start_bound and end_bound methods of the range (which can be inclusive or exclusive) and computing the corresponding length of the key.

Finally, we print out the key range. Note that we are assuming here that all the keys are strings, but the approach can be easily adapted for other types of keys.