The priority_queue crate in Rust provides an implementation of a priority queue based on a hashmap. Every item (or key) that is inserted is mapped to a hash value, using hashing, and a priority is assigned to it. In this way, a hashmap stores the data in the form of key-value pairs.
The following commonly used functions are provided in this crate:
push(item, priority): An item is inserted in the priority queue that has the specified priority. The key should be of a type that implements the Hash and Eq traits because a hashmap is being used under the hood.
pop(): The item with the highest priority is removed from the queue and returned. The item returned is of type Option. If the queue is empty, None is returned.
peek(): The item with the highest priority is only returned without being removed.
change_priority(item, new_priority): The item is looked up in the hashmap and, if it is found, the new priority is assigned to it and the old priority is returned; otherwise, the function returns None.
use priority_queue::PriorityQueue;fn main() {let mut q = PriorityQueue::new();// Add elements to an empty queue:assert!(q.is_empty());q.push("Maths", 10);q.push("Physics", 5);q.push("Chemistry", 15);// Check if Chemistry has the highest priority:assert_eq!(q.peek(), Some((&"Chemistry", &15)));// Give highest priority to Maths:q.change_priority("Maths", 20);// Check if Maths has the highest priority:assert_eq!(q.peek(), Some((&"Maths", &20)));}
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