Implement a fixed-size queue data structure that stores integers. The queue should have a maximum size and support enqueue and dequeue operations. Return -1 when trying to dequeue from an empty queue or enqueue to a full queue.

Examples:

Input: operations = [
    'enqueue 1',  // returns 1
    'enqueue 2',  // returns 2
    'enqueue 3',  // returns -1 (queue is full, size=2)
    'dequeue',    // returns 1
    'enqueue 3',  // returns 3
    'dequeue'     // returns 2
]
maxSize = 2
Output: [1, 2, -1, 1, 3, 2]
Explanation: Queue operations with max size 2, showing return values for each operation

Input: operations = [
    'dequeue',    // returns -1 (empty queue)
    'enqueue 1',  // returns 1
    'dequeue'     // returns 1
]
maxSize = 1
Output: [-1, 1, 1]
Explanation: Queue operations with max size 1, starting with dequeue on empty queue

Method used to process your code

public static List<Integer> processQueueOperations(List<String> operations, Integer maxSize) {
	FixedSizeQueue queue = new FixedSizeQueue(maxSize);
	List<Integer> results = new List<Integer>();

	for (String operation : operations) {
		if (operation.startsWith('enqueue')) {
			Integer item = Integer.valueOf(operation.split(' ')[1]);
			results.add(queue.enqueue(item));
		} else if (operation == 'dequeue') {
			results.add(queue.dequeue());
		}
	}

	return results;
}

Apex Code Editor

Welcome to Lightning Challenge!

Create an Account

Create account

How It Works

• Write your solution in the code editor
• Connect your Salesforce org to test
• Submit to check if your solution passes
• Use hints if you get stuck

Contest Alert

🏆 #CodeEveryDay Feb 2026

Contest runs February 1 - 28. Complete challenges to climb the leaderboard!

Points are calculated for challenges completed during the contest period.