A queue uses FIFO (first-in-first-out) ordering, that is, items are removed from the queue in the same order that they are added, like a line.
Queues can be used whenever is necessary to process things in that order (FIFO), like requests to a single shared resource, CPU scheduling, also helps in algorithms of other data structures, such as breadth-first search in graphs.
Representation
A queue can be implemented using an array or a linked list, can be either fixed or dynamic size.
Basic operations
- Add - Add an item to the end of the queue, also called enqueue.
- Remove - Remove the first item from the queue, also called dequeue.
- Peek - Return the top of the queue, without removing it.
- isEmpty - Return true if the queue is empty.
- isFull - Return true if the stack is full, used when the queue is fixed size.
Here's an implementation of a queue using an array, in TypeScript an array doesn't have a fixed length, so the operation isFull is not required, however, you can implement a queue with a fixed length and use that operation.
class Queue<T> {
private array: T[] = [];
add(data: T): void {
this.array.push(data);
}
remove(): T | undefined {
if (this.isEmpty()) throw new EmptyQueueException();
return this.array.shift();
}
peek(): T {
if (this.isEmpty()) throw new EmptyQueueException();
return this.array[0];
}
isEmpty(): boolean {
return this.array.length === 0;
}
}
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