Revision Guide: Stack

A stack is a linear data structure following LIFO, allowing addition/removal at one end.

Last-In-First-Out principle states that the last added element is the first to be removed.

PUSH adds an element to the top of the stack, expanding its size until full (overflow).

POP removes the topmost element from the stack. An empty stack leads to underflow condition.

Stacks manage function calls in programming, such as tracking local variables and execution states.

Stacks validate parentheses in expressions by pushing opening and ensuring correct nesting.

To reverse a string, push characters onto a stack, then pop them for output in reverse order.

Stacks can be implemented using Python lists with built-in methods append() and pop().

Use stacks to evaluate postfix notation by pushing operands and applying operators as they appear.

Convert infix expressions to postfix using stacks to manage operator precedence and parentheses.

Operating systems use stacks for memory management, allocating space for different processes.

Infix notation places operators between operands, e.g., A + B.

Prefix notation places operators before operands, e.g., +AB.

Postfix notation places operators after operands, e.g., AB+.

A stack can overflow only when full and underflow when empty; both conditions must be handled.

Stacks keep track of visited pages, enabling back-button functionality by retrieving last pages.

Initialize a stack with an empty list. Use append() to add and pop() to remove elements.

Underflow occurs when attempting to pop from an empty stack, raising an error.

A stack is full when it cannot accept more elements, normally handled via overflow management.

Real-world examples include stacks of plates, books, or any stacked items processed LIFO.

Stacks are widely used in algorithms, backtracking problems, and memory management.