Must-do problems: Queues and Stacks

150 min · Intermediate

Back to syllabus (Queues, Stacks & Priority Queues)

Each problem is solved by asking one question: which value must come out next? The oldest means a queue, the newest means a stack, either end means a deque, and the most important means a priority queue. Read the input with Scanner, solve every problem with the right structure from java.util, and run every test before opening a hint.

What you will learn

Choose a queue, a stack, a deque or a priority queue from the order a problem needs
Solve matching and undo problems with a stack
Simulate waiting lines with a queue and a priority queue
Use a heap for top-K and a deque for sliding-window problems

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