Below is a high-yield, pattern-driven set of queue problems. This focuses on the core use cases:

FIFO processing
BFS (trees & graphs)
level-by-level traversal
multi-source expansion
monotonic deque (advanced queue)
simulation / scheduling

1. Basic Queue / FIFO Simulation

Core Skill

Process items in order of arrival

Problems

Implement Queue using Stacks
Number of Recent Calls

Concepts

FIFO behavior
removing outdated elements

2. Tree BFS (Level Order)