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HashMap (update (overwrite old value (use std::collections::HashMap; let…

HashMap

update

overwrite old value

use std::collections::HashMap;

let scores = HashMap::new();
scores.insert(String::from("blue"), 10);
scores.insert(String::from("yellow"), 25);

insert value if the key has no value

use std::collections::HaspMap;

let scores = HashMap::new();
scores.insert(String::from("blue"), 10);

scores.entry(String::from("yellow")).or_insert(50);
scores.entry(String::from("blue")).or_insert(50);

base on old value

use std::collections::HashMap;

let text = "hello world wonderful world";
let map = HashMap::new();

for word in text.split_whitespace() {
    let count = map.entry(word).or_insert(0);
    *count += 1;
}

create

use std::collections::HashMap;

let mut s = HashMap::new();

s.insert(String::from("blue"), 10);
s.insert(String::from("blue"), 25);

use std::collections::HashMap;
let teams = vec![String::from("blue"), String::from("yellow")];
let initial_scores = vec![10, 50];

let scores: HashMap<_, _> = teams.iter().zip(initial_scores.iter()).collect();

access value

get() method

use std::collections::HashMap;

let scores = HaspMap::new();
scores.insert(String::from("yellow"), 10);
scores.insert(String::from("blue"), 50);

let team_name = String::from("blue");
let score = scores.get(&team_name);

for loop

use std::collections::HashMap;

let scores = HaspMap::new();
scores.insert(String::from("blue"), 10);
scores.insert(String::from("yellow"), 50);

for (key, value) in &scores {
    println!("{}: {}", key, value);
}