Rust code shared from the playground

playground.rs

use std::collections::HashMap;

fn make_freq_table<'a>(
    data: &'a [u16],
    counter: HashMap<&'a u16, usize>,
) -> HashMap<&'a u16, usize> {
    let mut c = counter;
    for x in data {
        let entry = c.entry(x).or_insert(0);
        *entry += 1;
    }
    c
}

fn main() {
    let mut c = HashMap::new();
    let data = &[1, 2, 3, 4, 5];
    c = make_freq_table(data, c);
    c = make_freq_table(data, c);
    c = make_freq_table(data, c);
    println!("{:?}", c);
}

Update counter.

Take data and HashMap, update HashMap, return HashMap.