find the largest key in a map in rust

To find the largest key in a Rust HashMap, you can iterate over the keys with a provided function keys() and use the max() function to return the largest key.

Here's an example:

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

fn main() {
    let mut map = HashMap::new();
    map.insert(1, "one");
    map.insert(3, "three");
    map.insert(2, "two");

    let largest_key = map.keys().max().unwrap();
    println!("The largest key is: {}", largest_key);
}
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In this example, we create a new HashMap and insert some key-value pairs. Then, we use the keys() function to get an iterator over the keys, and the max() function from the Iterator trait to find the largest key. Finally, we print out the largest key using println!().