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use std::collections::VecDeque;
#[derive(Eq, PartialEq, Debug)]
pub enum Element<T> {
Added,
NotAdded(T),
}
pub trait TryPush<T> {
fn try_push(&mut self, elem: T) -> Element<T>;
fn try_push_front(&mut self, elem: T) -> Element<T>;
}
impl<T> TryPush<T> for Vec<T> {
fn try_push(&mut self, elem: T) -> Element<T> {
if self.capacity() == self.len() {
Element::NotAdded(elem)
} else {
self.push(elem);
Element::Added
}
}
fn try_push_front(&mut self, elem: T) -> Element<T> {
if self.capacity() == self.len() || self.len() > 0 {
Element::NotAdded(elem)
} else {
self.push(elem);
Element::Added
}
}
}
impl<T> TryPush<T> for VecDeque<T> {
fn try_push(&mut self, elem: T) -> Element<T> {
if self.capacity() == self.len() {
Element::NotAdded(elem)
} else {
self.push_back(elem);
Element::Added
}
}
fn try_push_front(&mut self, elem: T) -> Element<T> {
if self.capacity() == self.len() {
Element::NotAdded(elem)
} else {
self.push_front(elem);
Element::Added
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn should_not_add_to_empty_vec() {
assert_eq!(Vec::with_capacity(0).try_push(1), Element::NotAdded(1));
}
#[test]
fn should_add_to_capable_vec() {
assert_eq!(Vec::with_capacity(10).try_push(1), Element::Added);
}
#[test]
fn should_not_add_front_to_empty_vec() {
assert_eq!(Vec::with_capacity(0).try_push_front(1), Element::NotAdded(1));
}
#[test]
fn should_not_add_front_to_non_empty_vec() {
assert_eq!(vec![0, 1].try_push_front(1), Element::NotAdded(1));
}
#[test]
fn should_add_front_to_capable_vec() {
assert_eq!(Vec::with_capacity(10).try_push_front(1), Element::Added);
}
#[test]
fn should_not_add_to_empty_vec_deque() {
let mut vd = VecDeque::with_capacity(0);
vd.push_back(1);
assert_eq!(vd.try_push(1), Element::NotAdded(1));
}
#[test]
fn should_add_to_capable_vec_deque() {
assert_eq!(VecDeque::with_capacity(10).try_push(1), Element::Added);
}
#[test]
fn should_not_add_front_to_empty_vec_deque() {
let mut vd = VecDeque::with_capacity(0);
vd.push_back(1);
assert_eq!(vd.try_push_front(1), Element::NotAdded(1));
}
#[test]
fn should_add_front_to_capable_vec_deque() {
assert_eq!(VecDeque::with_capacity(10).try_push_front(1), Element::Added);
}
}