Solution.rs

use std::collections::HashSet;
use rand::Rng;

struct RandomizedSet {
    list: HashSet<i32>
}


/**
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
impl RandomizedSet {

    fn new() -> Self {
        Self {
            list: HashSet::new()
        }
    }

    fn insert(&mut self, val: i32) -> bool {
        self.list.insert(val)
    }

    fn remove(&mut self, val: i32) -> bool {
        self.list.remove(&val)
    }

    fn get_random(&self) -> i32 {
        let i = rand::thread_rng().gen_range(0, self.list.len());
        *self.list.iter().collect::<Vec<&i32>>()[i]
    }
}

/**
 * Your RandomizedSet object will be instantiated and called as such:
 * let obj = RandomizedSet::new();
 * let ret_1: bool = obj.insert(val);
 * let ret_2: bool = obj.remove(val);
 * let ret_3: i32 = obj.get_random();
 */