Queue Practice Questions
A curated set of queue problems. These cover the patterns you’ll see in interviews and real systems: queue design, sliding windows, BFS in disguise, and stack-from-queue tricks.
Notice how often the answer is “use a deque.” That’s not a coincidence — a deque is the most flexible queue variant, and most “queue” problems really want either O(1) on both ends or a monotonic deque.
Easy
| Problem | Pattern | Status |
|---|---|---|
| Implement Stack using Queues | Two-queue / one-queue | Available |
| Design Circular Queue | Modular array | Available |
| Number of Recent Calls | Sliding window | Available |
Medium
| Problem | Pattern | Status |
|---|---|---|
| Sliding Window Maximum | Monotonic deque | Available |
| First Non-Repeating Character in a Stream | Queue + frequency map | Available |
| Rotting Oranges | Multi-source BFS | Available |
More Practice (Coming Soon)
| Problem | Pattern | Status |
|---|---|---|
| Walls and Gates | Multi-source BFS | Coming Soon |
| Open the Lock | BFS over states | Coming Soon |
| Perfect Squares | BFS | Coming Soon |
| Task Scheduler | Priority queue | Coming Soon |
| Reveal Cards in Increasing Order | Deque simulation | Coming Soon |
| Snakes and Ladders | BFS | Coming Soon |