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Get basic incomplete Python queue API working

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This commit is contained in:
Michael Bradley 2025-01-08 22:52:25 +13:00
parent 661e1d220a
commit 0995e6db90
Signed by: MichaelBradley
SSH key fingerprint: SHA256:cj/YZ5VT+QOKncqSkx+ibKTIn0Obg7OIzwzl9BL8EO8
8 changed files with 69 additions and 45 deletions
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45
src/backing/pure/binary_heap.rs
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@ -4,7 +4,7 @@ use super::PureBacking;
/// A binary min-heap backed by an array
#[derive(Debug)]
pub struct BinaryHeap<T: Ord + Copy> {
pub struct BinaryHeap<T: Ord + Clone + Send + Sync> {
data: Vec<T>,
}
@ -33,18 +33,23 @@ impl fmt::Display for SiftError {
/// Whether a sift operation succeeded
type SiftResult = Result<(), SiftError>;
impl<T: Ord + Copy> BinaryHeap<T> {
impl<T: Ord + Clone + Send + Sync> BinaryHeap<T> {
/// Instantiates a new (empty) binary heap
pub fn new() -> Self {
Self { data: vec![] }
}
/// Fix an index representing a node with valid children but that may violate the heap property compared to its immediate parent
fn sift_up(&mut self, i: usize) -> SiftResult {
if i == 0 {
// Base case, at root so nothing to do
Ok(())
} else if let Some(child) = self.data.get(i).copied() {
} else if let Some(child) = self.data.get(i).cloned() {
let parent_index = (i - 1) / 2;
// Check if the heap property is violated
if child < self.data[parent_index] {
// Swap child with parent
self.data[i] = self.data[parent_index];
self.data[i] = self.data[parent_index].clone();
self.data[parent_index] = child;
// Repeat process with parent
@ -64,12 +69,12 @@ impl<T: Ord + Copy> BinaryHeap<T> {
// Tried to sift a non-existent index
Err(SiftError::new(i, self.data.len()))
} else {
if let Some(first_child) = self.data.get(i * 2 + 1).copied() {
if let Some(first_child) = self.data.get(i * 2 + 1).cloned() {
let smaller_child_index;
let smaller_child;
// Find the smallest child and its index
if let Some(second_child) = self.data.get(i * 2 + 2).copied() {
if let Some(second_child) = self.data.get(i * 2 + 2).cloned() {
// Both children, use the smaller one
if first_child < second_child {
smaller_child = first_child;
@ -86,7 +91,7 @@ impl<T: Ord + Copy> BinaryHeap<T> {
if smaller_child < self.data[i] {
// Swap parent with child
self.data[smaller_child_index] = self.data[i];
self.data[smaller_child_index] = self.data[i].clone();
self.data[i] = smaller_child;
// Repeat process with child
@ -103,23 +108,19 @@ impl<T: Ord + Copy> BinaryHeap<T> {
}
}
impl<T: Ord + Copy> FromIterator<T> for BinaryHeap<T> {
impl<T: Ord + Clone + Send + Sync> FromIterator<T> for BinaryHeap<T> {
fn from_iter<U: IntoIterator<Item = T>>(iter: U) -> Self {
let mut this = Self {
data: Vec::from_iter(iter),
};
for i in (0..=(this.data.len() / 2)).rev() {
this.sift_down(i);
this.sift_down(i).expect("Index error during heapify");
}
this
}
}
impl<T: Ord + Copy> PureBacking<T> for BinaryHeap<T> {
fn new() -> Self {
Self { data: vec![] }
}
impl<T: Ord + Clone + Send + Sync> PureBacking<T> for BinaryHeap<T> {
fn add(&mut self, item: T) {
// Append item
self.data.push(item);
@ -132,22 +133,18 @@ impl<T: Ord + Copy> PureBacking<T> for BinaryHeap<T> {
// No extra processing
0 | 1 => self.data.pop(),
_ => {
let last = self
// Get the original root
let root = self.data[0].clone();
// Move final item to the root and sift down to regain heap property
self.data[0] = self
.data
.pop()
.expect("Vector claimed not to be empty but was");
let root = self
.data
.get_mut(0)
.expect("Vector claimed to have multiple items but didn't");
// Move final item to the root and sift down to regain heap property
let best = *root;
*root = last;
self.sift_down(0).unwrap();
// Return original root
Some(best)
Some(root)
}
}
}