map Iterate in Rust 1.55

In Rust, iterating over a hash (or HashMap) is done using its iter() method, which returns an iterator of key-value pairs. Here's an example:

use std::collections::HashMap;
fn main() {

    let mut scores = HashMap::new();

    scores.insert("Alice", 92);

    scores.insert("Bob", 85);

    scores.insert("Charlie", 78);

    

    for (key, value) in &scores {

        println!("{}: {}", key, value);

    }

}

In this example, we first create a new HashMap called scores and insert three key-value pairs into it. Then we use a for loop to iterate over the HashMap using the &scores reference, which allows us to borrow the HashMap immutably.

Inside the loop, we use pattern matching to destructure each key-value pair into its constituent parts: key and value. We then print these values to the console using println!().

The output of this program should be:

Alice: 92
Charlie: 78
Bob: 85

Note that the order of the key-value pairs may be different than the order in which they were inserted into the HashMap, since the HashMap does not maintain any particular order.