What are the main functions of a stack?

A stack is a data structure that operates on the Last In, First Out (LIFO) principle, meaning the last element added is the first to be removed.

Main functions of a stack:

• push(element) — adds an element to the top of the stack.
• pop() — removes and returns the element from the top of the stack.
• peek() or top() — returns the element at the top of the stack without removing it.
• isEmpty() — checks if the stack is empty.

Example in Kotlin:

val stack = mutableListOf<Int>()

// Add an element
stack.add(10) // push

// Get the top element
val top = stack.last() // peek

// Remove the top element
val removed = stack.removeAt(stack.size - 1) // pop

// Check if empty
val empty = stack.isEmpty()