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use std::{
collections::{BTreeMap, HashMap}, sync::Arc,
};
#[derive(Debug, Clone, PartialEq)]
pub struct RollingSet<T: std::hash::Hash + std::cmp::Eq> {
i: usize,
cap: usize,
i_val_ordered: BTreeMap<usize, Arc<T>>,
val_i: HashMap<Arc<T>, usize>,
}
impl<T> RollingSet<T>
where
T: Eq + std::hash::Hash,
{
pub fn new(cap: usize) -> Self {
Self {
cap,
i: 0,
i_val_ordered: BTreeMap::new(),
val_i: HashMap::new(),
}
}
pub fn with_capacity(cap: usize) -> Self {
Self {
cap,
i: 0,
i_val_ordered: BTreeMap::new(),
val_i: HashMap::with_capacity(cap),
}
}
pub fn insert(&mut self, element: T) {
self.i += 1;
let v = Arc::new(element);
self.i_val_ordered.insert(self.i, v.clone());
self.val_i.insert(v, self.i);
if self.len() > self.cap {
let first = self.i_val_ordered.first_key_value().unwrap().0;
let v = self.i_val_ordered.get(&first).unwrap();
self.val_i.remove(v);
}
}
pub fn remove(&mut self, element: &T) -> bool {
let i = match self.val_i.get(element) {
Some(i) => i,
None => return false,
};
self.i_val_ordered.remove(i);
self.val_i.remove(element);
true
}
pub fn contains(&self, element: &T) -> bool {
self.val_i.contains_key(element)
}
pub fn len(&self) -> usize {
self.val_i.len()
}
pub fn clear(&mut self) {
self.i_val_ordered.clear();
self.val_i.clear();
}
}
#[cfg(test)]
mod tests {
use crate::RollingSet;
#[test]
fn create() {
let mut set = RollingSet::new(100);
set.insert("one");
set.insert("two");
set.insert("three");
assert!(set.contains(&"one"));
assert!(set.contains(&"two"));
assert!(set.contains(&"three"));
assert!(!set.contains(&"four"));
}
#[test]
fn roll() {
let mut set = RollingSet::new(3);
set.insert("one");
set.insert("two");
set.insert("three");
set.insert("four");
assert!(set.len() == 3);
assert!(!set.contains(&"one"));
assert!(set.contains(&"two"));
assert!(set.contains(&"three"));
assert!(set.contains(&"four"));
}
#[test]
fn remove() {
let mut set = RollingSet::new(3);
set.insert("one");
set.insert("two");
set.insert("three");
set.insert("four");
assert!(set.contains(&"two"));
assert!(set.contains(&"three"));
assert!(set.contains(&"four"));
set.remove(&"two");
assert!(set.len() == 2);
assert!(!set.contains(&"two"));
assert!(set.contains(&"three"));
assert!(set.contains(&"four"));
}
}