A stack is a fundamental data structure in computer science and programming that follows the Last-In-First-Out (LIFO) principle. In a stack, the last element added is the first one to be removed. Think of it like a stack of plates: you add plates to the top of the stack, and when you want to remove a plate, you take it from the top.
Key characteristics of a stack:
- LIFO (Last-In-First-Out) Principle: The most recently added element is the first one to be removed. It’s like a stack of items where you can only interact with the top item.
- Two Primary Operations:
- Push: Adding an element to the top of the stack.
- Pop: Removing the top element from the stack.
- Peek or Top: Viewing the top element without removing it.
- Empty Stack: A stack can be empty, meaning it contains no elements.
- Size: The number of elements in the stack.
Common use cases for stacks
- Function Call Stack: In many programming languages, the function call stack is implemented as a stack data structure. When a function is called, its information is pushed onto the stack, and when it returns, it is popped off the stack.
- Expression Evaluation: Stacks are used to evaluate expressions, especially in languages that use postfix or prefix notation (e.g., Reverse Polish Notation).
- Undo/Redo Functionality: Stacks are used to implement undo and redo operations in applications like text editors.
- Backtracking Algorithms: Algorithms that involve backtracking, like depth-first search (DFS), often use stacks to keep track of the search path.
- Syntax Parsing: Stacks are used in parsing and interpreting languages to keep track of symbols and their relationships.
- Memory Management: Stacks are used in memory allocation and deallocation, especially in languages like C/C++.
Stacks can be implemented using various underlying data structures, such as arrays or linked lists. The choice of implementation depends on the specific use case and the programming language being used.
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