Making a practical priority queue from std::collections::BinaryHeap

priorityqueue.rs

use std::collections::BinaryHeap;

// Create a type that implements Ord to represent your tasks. That can be
// fed into BinaryHeap with a tuple, using its first field representing priority,
//
// > "When derived on enums, variants are ordered by their discriminants"
// > - https://doc.rust-lang.org/std/cmp/trait.PartialOrd.html#derivable
#[derive(Debug, Ord, PartialOrd, PartialEq, Eq)]
enum Task {
    A,
    B,
    C,
}

// You might like to implement PartialOrd yourself, rather than having 
// the different task categories be able to out-rank each other:

// impl PartialOrd for Task {
//     fn partial_cmp(&self, _: &Task) -> Option<std::cmp::Ordering> {
//         Some(std::cmp::Ordering::Equal)
//     }
// }

fn main() {
    let mut queue = BinaryHeap::new();

    queue.push((1, Task::A));
    queue.push((1, Task::B));
    queue.push((2, Task::C));
    queue.push((0, Task::C));
    queue.push((1, Task::A));
    queue.push((1, Task::C));
    
    while let Some((priority, task)) = queue.pop() {
        println!("{_priority} {task:?}");
    }
}

Usage is explained in this video: https://youtu.be/nCNjzoKHtHk