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use alloc::format;
use alloc::vec;
use alloc::vec::Vec;
/// Queue data structure
#[derive(Debug)]
pub struct Queue<T> {
// data
data: Vec<T>,
// the queue head pointer
head: usize,
// the queue tail pointer
tail: usize,
// the queue size
len: usize,
}
impl<T: Clone + Default> Queue<T> {
/// Create an empty queue of fixed size
///
/// ```rust
/// use algorithms_rs::Queue;
///
/// let empty_queue = Queue::<i32>::new(1);
///
/// assert_eq!(empty_queue.is_empty(), true);
/// ```
pub fn new(length: usize) -> Self {
let data = vec![T::default(); length];
Self {
data,
head: 0,
tail: 0,
len: length,
}
}
/// Determine if queue is empty
///
/// ```rust
/// use algorithms_rs::Queue;
///
/// let empty_queue = Queue::<i32>::new(1);
///
/// assert_eq!(empty_queue.is_empty(), true);
/// ```
pub fn is_empty(&self) -> bool {
self.head == self.tail
}
/// Enter the queue from the end of the queue
///
/// ```rust
/// use algorithms_rs::Queue;
///
/// let mut queue = Queue::<i32>::new(3);
///
/// queue.en_queue(1);
/// queue.en_queue(2);
///
/// assert_eq!(queue.is_empty(), false);
/// ```
pub fn en_queue(&mut self, element: T) -> anyhow::Result<()> {
if self.head == (self.tail + 1) % self.len {
return Err(anyhow::anyhow!("overflow"));
}
if let Some(value) = self.data.get_mut(self.tail) {
*value = element;
} else {
return Err(anyhow::anyhow!(format!(
"get index of {} element",
self.tail
)));
}
if self.tail == (self.len - 1) {
self.tail = 0;
} else {
self.tail += 1;
}
Ok(())
}
/// From the head of the queue Out of the queue
///
/// ```rust
/// use algorithms_rs::Queue;
///
/// let mut queue = Queue::<i32>::new(3);
///
/// queue.en_queue(1);
/// queue.en_queue(2);
///
/// queue.de_queue();
/// queue.de_queue();
///
/// assert_eq!(queue.is_empty(), true);
/// ```
pub fn de_queue(&mut self) -> anyhow::Result<T> {
if self.is_empty() {
return Err(anyhow::anyhow!("underflow"));
}
let element = self.data.get(self.head);
if self.head == (self.len - 1) {
self.head = 0;
} else {
self.head += 1;
}
Ok(element.unwrap().clone())
}
}
#[cfg(test)]
mod tests {
use super::*;
fn process_result<T>(result: Result<T, anyhow::Error>) {
match result {
Ok(_value) => {}
Err(err) => {
if err.to_string() == *"overflow" {
assert_eq!(err.to_string(), "overflow".to_string());
} else if err.to_string() == *"underflow" {
assert_eq!(err.to_string(), "underflow".to_string());
}
}
}
}
#[test]
fn test_is_empty_queue() {
let empty_queue = Queue::<i32>::new(3);
assert!(empty_queue.is_empty());
}
#[test]
fn test_is_enqueue_success() {
let mut queue = Queue::<i32>::new(3);
let ret = queue.en_queue(1);
process_result(ret);
let ret = queue.en_queue(2);
process_result(ret);
}
#[test]
fn test_is_enqueue_overflow() {
let mut queue = Queue::<i32>::new(3);
let ret = queue.en_queue(1);
process_result(ret);
let ret = queue.en_queue(2);
process_result(ret);
let ret = queue.en_queue(3);
process_result(ret);
}
#[test]
fn test_is_dequeue_success() {
let mut queue = Queue::<i32>::new(3);
let ret = queue.en_queue(1);
process_result(ret);
let ret = queue.en_queue(2);
process_result(ret);
let ret = queue.de_queue();
process_result(ret);
let ret = queue.de_queue();
process_result(ret);
let ret = queue.en_queue(4);
process_result(ret);
let ret = queue.de_queue();
process_result(ret);
let ret = queue.en_queue(5);
process_result(ret);
let ret = queue.en_queue(6);
process_result(ret);
let ret = queue.de_queue();
process_result(ret);
let ret = queue.de_queue();
process_result(ret);
let ret = queue.en_queue(7);
process_result(ret);
let ret = queue.en_queue(8);
process_result(ret);
}
}