Topic 7 Stack

🧑‍💻 Introduction to Stack

A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. Think of it like a stack of plates 🍽️ — you always add new plates on top and take the top one off first.

Stacks are powerful tools used to solve a variety of problems efficiently. They’re like a magic box 🧙‍♂️ for handling nested structures, evaluating expressions, and keeping track of previous elements in many algorithms.

⚡ Key Operations of a Stack

• Push: Add an element to the top of the stack 🆙

• Pop: Remove the top element from the stack 🔽

• Peek or Top: Look at the top element without removing it 👀

• IsEmpty: Check if the stack is empty 🚫

• Size: Get the number of elements in the stack 📏

💡 Where are Stacks Used?

Stacks are commonly used in scenarios like:

• Expression evaluation (e.g., arithmetic expressions, reverse Polish notation) ➗

• Parsing and backtracking (e.g., balanced parentheses) 🧩

• Depth-first search (DFS) in graph traversal 🌲

They can be implemented using arrays or linked lists, and many algorithms rely on stack-based operations to solve problems effectively.

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📝 Problems in the Stack Topic

1. Valid Parentheses Problem URL: LeetCode - Valid Parentheses Study here 📘
2. Simplify Path Problem URL: LeetCode - Simplify Path Study here 📘
3. Min Stack Problem URL: LeetCode - Min Stack Study here 📘
4. Evaluate Reverse Polish Notation Problem URL: LeetCode - Evaluate Reverse Polish Notation Study here 📘
5. Basic Calculator Problem URL: LeetCode - Basic Calculator Study here 📘

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🎉 Conclusion

Congrats on diving into stacks! 🎊 Stacks are a fundamental data structure that can help you solve problems efficiently in various scenarios, like evaluating expressions, navigating through nested structures, and backtracking. 🚀

Take your time exploring each problem and its solution. You'll see how stacks can make even the trickiest problems simpler and more manageable! 😊

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✨ Happy coding! 💻✨