+//! A priority queue implemented with a 4-ary heap.
+//!
+//! Insertion and popping the minimal element have `O(log n)` time complexity.
+//! Checking the minimal element is `O(1)`. Keys of elements in the heap can
+//! also be increased or decreased
+//!
+//! # Examples
+//!
+//! ```
+//! use stud_rust_base::index_heap::{Indexing, IndexdMinHeap};
+//!
+//! #[derive(Copy, Clone, Eq, PartialEq, Debug, Ord, PartialOrd)]
+//! pub struct State {
+//! pub distance: usize,
+//! pub node: usize,
+//! }
+//!
+//!
+//! // The `Indexing` traits needs to be implemented as well, so we can find elements to decrease their key.
+//! impl Indexing for State {
+//! fn as_index(&self) -> usize {
+//! self.node as usize
+//! }
+//! }
+//!
+//! fn main() {
+//! let mut heap = IndexdMinHeap::new(3);
+//! heap.push(State { node: 0, distance: 42 });
+//! heap.push(State { node: 1, distance: 23 });
+//! heap.push(State { node: 2, distance: 50000 });
+//! assert_eq!(heap.peek().cloned(), Some(State { node: 1, distance: 23 }));
+//! heap.decrease_key(State { node: 0, distance: 1 });
+//! assert_eq!(heap.pop(), Some(State { node: 0, distance: 1 }));
+//! }
+//!
+//! ```
+
use std;
use std::cmp::min;
use std::mem::swap;
use std::ptr;
+/// A trait to map elements in a heap to a unique index.
+/// The element type of the `IndexdMinHeap` has to implement this trait.
pub trait Indexing {
+ /// This method has to map a heap element to a unique `usize` index.
fn as_index(&self) -> usize;
}
-// A priority queue where the elements are IDs from 0 to id_count-1 where id_count is a number that is set in the constructor.
-// The elements are sorted by integer keys.
+/// A priority queue where the elements are IDs from 0 to id_count-1 where id_count is a number that is set in the constructor.
+/// The elements are sorted ascending by the ordering defined by the `Ord` trait.
+/// The interface mirros the standard library BinaryHeap (except for the reversed order).
+/// Only the methods necessary for dijkstras algorithm are implemented.
+/// In addition, `increase_key` and `decrease_key` methods are available.
#[derive(Debug)]
pub struct IndexdMinHeap<T: Ord + Indexing> {
positions: Vec<usize>,
const INVALID_POSITION: usize = std::usize::MAX;
impl<T: Ord + Indexing> IndexdMinHeap<T> {
- pub fn new(max_id: usize) -> IndexdMinHeap<T> {
+ /// Creates an empty `IndexdMinHeap` as a min-heap.
+ /// The indices (as defined by the `Indexing` trait) of all inserted elements
+ /// will have to be between in `[0, max_index)`
+ pub fn new(max_index: usize) -> IndexdMinHeap<T> {
IndexdMinHeap {
- positions: vec![INVALID_POSITION; max_id],
+ positions: vec![INVALID_POSITION; max_index],
data: Vec::new()
}
}
+ /// Returns the length of the binary heap.
pub fn len(&self) -> usize {
self.data.len()
}
+ /// Checks if the binary heap is empty.
pub fn is_empty(&self) -> bool {
self.len() == 0
}
+ /// Checks if the heap already contains an element mapped to the given index
pub fn contains_index(&self, id: usize) -> bool {
self.positions[id] != INVALID_POSITION
}
+ /// Drops all items from the heap.
pub fn clear(&mut self) {
for element in &self.data {
self.positions[element.as_index()] = INVALID_POSITION;
self.data.clear();
}
+ /// Returns a reference to the smallest item in the heap, or None if it is empty.
pub fn peek(&self) -> Option<&T> {
self.data.first()
}
+ /// Removes the greatest item from the binary heap and returns it, or None if it is empty.
pub fn pop(&mut self) -> Option<T> {
self.data.pop().map(|mut item| {
self.positions[item.as_index()] = INVALID_POSITION;
})
}
+ /// Pushes an item onto the binary heap.
+ /// Panics if an element with the same index already exists.
pub fn push(&mut self, element: T) {
assert!(!self.contains_index(element.as_index()));
let insert_position = self.len();
self.move_up_in_tree(insert_position);
}
- // Updates the key of an element if the new key is smaller than the old key.
- // Does nothing if the new key is larger.
- // Undefined if the element is not part of the queue.
+ /// Updates the key of an element if the new key is smaller than the old key.
+ /// Does nothing if the new key is larger.
+ /// Panics if the element is not part of the queue.
pub fn decrease_key(&mut self, element: T) {
let position = self.positions[element.as_index()];
self.data[position] = element;
self.move_up_in_tree(position);
}
- // Updates the key of an element if the new key is larger than the old key.
- // Does nothing if the new key is smaller.
- // Undefined if the element is not part of the queue.
+ /// Updates the key of an element if the new key is larger than the old key.
+ /// Does nothing if the new key is smaller.
+ /// Panics if the element is not part of the queue.
pub fn increase_key(&mut self, element: T) {
let position = self.positions[element.as_index()];
self.data[position] = element;
+//! This module contains a few traits and blanket implementations
+//! for (de)serializing and writing/reading numeric data to/from the disc.
+//! To use it you should import the `Load` and `Store` traits and use the
+//! `load_from` and `write_to` methods.
+//!
+//! # Example
+//!
+//! ```
+//! use stud_rust_base::io::*;
+//!
+//! fn test() {
+//! let head = Vec::<u32>::load_from("head_file_name").expect("could not read head");
+//! let lat = Vec::<f32>::load_from("node_latitude_file_name").expect("could not read lat");
+//! head.write_to("output_file").expect("could not write head");
+//! }
+//! ```
+
use std::fs;
use std::fs::File;
use std::io::prelude::*;
use std::mem;
use std::slice;
+/// A trait which allows accessing the data of an object as a slice of bytes.
+/// The bytes should represent a serialization of the object and allow
+/// recreating it when reading these bytes again from the disk.
+///
+/// Do not use this Trait but rather the `Store` trait.
pub trait DataBytes {
+ /// Should return the serialized object as a slice of bytes
fn data_bytes(&self) -> &[u8];
}
+/// A trait which mutably exposes the internal data of an object so that
+/// a serialized object can be loaded from disk and written back into a precreated
+/// object of the right size.
+///
+/// Do not use this Trait but rather the `Load` trait.
pub trait DataBytesMut {
+ /// Should return a mutable slice of the internal data of the object
fn data_bytes_mut(&mut self) -> &mut [u8];
}
}
}
+/// A trait which extends the `DataBytes` trait and exposes a method to write objects to disk.
pub trait Store : DataBytes {
+ /// Writes the serialized object to the file with the given filename
fn write_to(&self, filename: &str) -> Result<()> {
File::create(filename)?.write_all(self.data_bytes())
}
impl<T: DataBytes> Store for T {}
impl<T> Store for [T] where [T]: DataBytes {}
+/// A trait to load serialized data back into objects.
pub trait Load : DataBytesMut + Sized {
+ /// This method must create an object of the correct size for serialized data with the given number of bytes.
+ /// It should not be necessary to call this method directly.
fn new_with_bytes(num_bytes: usize) -> Self;
+ /// This method will load serialized data from the disk, create an object of the appropriate size,
+ /// deserialize the bytes into the object and return the object.
fn load_from(filename: &str) -> Result<Self> {
let metadata = fs::metadata(filename)?;
let mut file = File::open(filename)?;
+//! This module contains a few utilities to measure how long executing algorithms takes.
+//! It utilizes the `time` crate.
+
use time_crate as time;
+/// This function will measure how long it takes to execute the given lambda,
+/// print the time and return the result of the lambda.
pub fn report_time<Out, F: FnOnce() -> Out>(name: &str, f: F) -> Out {
let start = time::now();
println!("starting {}", name);
res
}
+/// This function will measure how long it takes to execute the given lambda
+/// and return a tuple of the result of the lambda and a duration object.
pub fn measure<Out, F: FnOnce() -> Out>(f: F) -> (Out, time::Duration) {
let start = time::now();
let res = f();
(res, time::now() - start)
}
+/// A struct to repeatedly measure the time passed since the timer was started
#[derive(Debug)]
pub struct Timer {
start: time::Tm
}
impl Timer {
+ /// Create and start a new `Timer`
pub fn new() -> Timer {
Timer { start: time::now() }
}
+ /// Reset the `Timer`
pub fn restart(&mut self) {
self.start = time::now();
}
+ /// Print the passed time in ms since the timer was started
pub fn report_passed_ms(&self) {
println!("{}ms", (time::now() - self.start).num_milliseconds());
}
+ /// Return the number of ms passed since the timer was started as a `i64`
pub fn get_passed_ms(&self) -> i64 {
(time::now() - self.start).num_milliseconds()
}
projects / Mitarbeiter / Tim-Zeitz / stud-rust-base.git / commitdiff