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use std::cmp::Ordering;
use std::fmt::Debug;
#[derive(Debug)]
pub struct HeapSelection<T: PartialOrd + Debug> {
k: usize,
n: usize,
sorted: bool,
heap: Vec<T>,
}
impl<'a, T: PartialOrd + Debug> HeapSelection<T> {
pub fn with_capacity(k: usize) -> HeapSelection<T> {
HeapSelection {
k,
n: 0,
sorted: false,
heap: Vec::new(),
}
}
pub fn add(&mut self, element: T) {
self.sorted = false;
if self.n < self.k {
self.heap.push(element);
self.n += 1;
if self.n == self.k {
self.sort();
}
} else {
self.n += 1;
if element.partial_cmp(&self.heap[0]) == Some(Ordering::Less) {
self.heap[0] = element;
self.sift_down(0, self.k - 1);
}
}
}
pub fn heapify(&mut self) {
let n = self.heap.len();
if n <= 1 {
return;
}
for i in (0..=(n / 2 - 1)).rev() {
self.sift_down(i, n - 1);
}
}
pub fn peek(&self) -> &T {
if self.sorted {
&self.heap[0]
} else {
&self
.heap
.iter()
.max_by(|a, b| a.partial_cmp(b).unwrap())
.unwrap()
}
}
pub fn peek_mut(&mut self) -> &mut T {
&mut self.heap[0]
}
pub fn get(self) -> Vec<T> {
self.heap
}
fn sift_down(&mut self, k: usize, n: usize) {
let mut kk = k;
while 2 * kk <= n {
let mut j = 2 * kk;
if j < n && self.heap[j].partial_cmp(&self.heap[j + 1]) == Some(Ordering::Less) {
j += 1;
}
if self.heap[kk].partial_cmp(&self.heap[j]) == Some(Ordering::Equal)
|| self.heap[kk].partial_cmp(&self.heap[j]) == Some(Ordering::Greater)
{
break;
}
self.heap.swap(kk, j);
kk = j;
}
}
fn sort(&mut self) {
self.sorted = true;
self.heap.sort_by(|a, b| b.partial_cmp(a).unwrap());
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn with_capacity() {
let heap = HeapSelection::<i32>::with_capacity(3);
assert_eq!(3, heap.k);
}
#[test]
fn test_add() {
let mut heap = HeapSelection::with_capacity(3);
heap.add(-5);
assert_eq!(-5, *heap.peek());
heap.add(333);
assert_eq!(333, *heap.peek());
heap.add(13);
heap.add(10);
heap.add(2);
heap.add(0);
heap.add(40);
heap.add(30);
assert_eq!(8, heap.n);
assert_eq!(vec![2, 0, -5], heap.get());
}
#[test]
fn test_add1() {
let mut heap = HeapSelection::with_capacity(3);
heap.add(std::f64::INFINITY);
heap.add(-5f64);
heap.add(4f64);
heap.add(-1f64);
heap.add(2f64);
heap.add(1f64);
heap.add(0f64);
assert_eq!(7, heap.n);
assert_eq!(vec![0f64, -1f64, -5f64], heap.get());
}
#[test]
fn test_add2() {
let mut heap = HeapSelection::with_capacity(3);
heap.add(std::f64::INFINITY);
heap.add(0.0);
heap.add(8.4852);
heap.add(5.6568);
heap.add(2.8284);
assert_eq!(5, heap.n);
assert_eq!(vec![5.6568, 2.8284, 0.0], heap.get());
}
#[test]
fn test_add_ordered() {
let mut heap = HeapSelection::with_capacity(3);
heap.add(1.);
heap.add(2.);
heap.add(3.);
heap.add(4.);
heap.add(5.);
heap.add(6.);
assert_eq!(vec![3., 2., 1.], heap.get());
}
}