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use std::iter::Extend;
use std::ops::Index;
#[derive(Debug, Default)]
pub struct StackVec<T: Default + Copy + std::fmt::Debug> {
len: usize,
array: [T; 32],
heap_vec: Vec<T>,
}
impl<T: Default + Copy + std::fmt::Debug> StackVec<T> {
pub fn new() -> Self {
StackVec {
len: 0,
array: [T::default(); 32],
heap_vec: Vec::new(),
}
}
pub fn push(&mut self, ind: T) {
if self.len == self.array.len() {
if self.heap_vec.is_empty() {
self.heap_vec.reserve(32);
for _ in 0..8 {
self.heap_vec.push(T::default());
}
}
self.heap_vec[0..8].copy_from_slice(&self.array);
self.heap_vec.push(ind);
} else if self.len > self.array.len() {
self.heap_vec.push(ind);
} else {
self.array[self.len] = ind;
}
self.len += 1;
}
pub fn pop(&mut self) -> Option<T> {
if self.len == 0 {
return None;
}
if self.len >= self.array.len() {
self.len -= 1;
self.heap_vec.pop()
} else {
let ret = self.array[self.len - 1];
self.len -= 1;
Some(ret)
}
}
pub fn len(&self) -> usize {
self.len
}
pub fn is_empty(&self) -> bool {
self.len == 0
}
pub fn iter(&self) -> StackVecIter<T> {
StackVecIter {
stack: &self,
range: 0..self.len,
}
}
}
pub struct StackVecIter<'a, T: Default + Copy + std::fmt::Debug> {
stack: &'a StackVec<T>,
range: std::ops::Range<usize>,
}
impl<'a, T: Default + Copy + std::fmt::Debug> Iterator for StackVecIter<'a, T> {
type Item = &'a T;
fn next(&mut self) -> Option<&'a T> {
if self.range.len() == 0 {
None
} else {
let idx = self.range.start;
self.range.start += 1;
Some(&self.stack[idx])
}
}
}
impl<'a, T: Default + Copy + std::fmt::Debug> std::iter::DoubleEndedIterator
for StackVecIter<'a, T>
{
fn next_back(&mut self) -> Option<&'a T> {
if self.range.len() == 0 {
None
} else {
let idx = self.range.end - 1;
self.range.end -= 1;
Some(&self.stack[idx])
}
}
}
impl<T: Default + Copy + std::fmt::Debug> Index<usize> for StackVec<T> {
type Output = T;
fn index(&self, idx: usize) -> &T {
if self.len >= self.array.len() {
&self.heap_vec[idx]
} else {
&self.array[idx]
}
}
}
impl<T: Default + Copy + std::fmt::Debug> Extend<T> for StackVec<T> {
fn extend<I>(&mut self, iter: I)
where
I: IntoIterator<Item = T>,
{
for elem in iter {
self.push(elem);
}
}
}
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