Stacks and Queues in Interviews

In many technical interviews, Stacks and Queues are rarely asked about directly. Instead, they are often used as intermediary tools to manage data in a way that aligns with the problem's requirements. The main challenge is recognizing when using one of these data structures can help you solve the problem. In most situations, you'll likely be able to use an array as a stack or queue rather than implementing these data structures from scratch. Here are some guidelines to help you determine whether to use a stack or a queue.

When to use a Stack

• Reversal Properties: If the problem involves reversing elements, such as in string reversal or undo operations in text editors.
• Balancing Symbols: Problems that require checking the balance of certain characters, like matching parenthesis, often benefit from a stack.
• Depth-First Search (DFS): We'll explore DFS in upcoming lessons when discussing Binary Trees. For now, be aware that stacks can be used to perform a depth-first search through tree or graph data structures.

Note that if a problem requires a stack, another approach could be using recursion, which uses a call stack to keep track of function calls. We'll learn about recursion in the next lesson.

When to use a Queue

• Order Maintenance: When the problem requires maintaining elements in their original order, such as in task scheduling or managing print jobs, a queue is usually suitable.
• Breadth-First Search (BFS): As with DFS, we'll explore BFS in the upcoming lesson on Binary Trees. You'll learn what BFS is and how queues can help us implement it.
• Buffering or Pipeline If the scenario requires a buffer of elements to be processed in the order they arrive, like in streaming data or load balancing, a queue offers the necessary structure.

By understanding these guidelines, you'll be better equipped to recognize when stacks or queues can be valuable tools in solving interview problems.