Collections Structs

Collection types structs

HashMap

use std::collections::HashMap;

fn main() {
    // Create
    let mut map: HashMap<String, i32> = HashMap::new();

    // Insert
    map.insert("Alice".to_string(), 100);
    map.insert("Bob".to_string(), 85);
    map.insert("Charlie".to_string(), 92);

    println!("Map: {:?}", map);

    // Get
    println!("\nAlice: {:?}", map.get("Alice"));
    println!("Unknown: {:?}", map.get("Unknown"));

    // Get mutable
    if let Some(score) = map.get_mut("Bob") {
        *score += 10;
    }
    println!("Bob after bonus: {:?}", map.get("Bob"));

    // Entry API
    map.entry("David".to_string()).or_insert(75);
    map.entry("Alice".to_string()).and_modify(|s| *s += 5);
    println!("After entry: {:?}", map);

    // Contains
    println!("\nContains Alice: {}", map.contains_key("Alice"));

    // Remove
    let removed = map.remove("Charlie");
    println!("Removed: {:?}", removed);

    // Iteration
    println!("\n=== Iteration ===");
    for (name, score) in &map {
        println!("{}: {}", name, score);
    }

    // Keys and values
    println!("\nKeys: {:?}", map.keys().collect::<Vec<_>>());
    println!("Values: {:?}", map.values().collect::<Vec<_>>());

    // Length
    println!("\nLength: {}", map.len());
}