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stacks

README.md

STACK

  • Stack is an ADT (abstract data type) that is a collection of elements where items are added and removed from the end, known as the "top" of the stack.

  • Stack works on the principle of LIFO (Last In First Out), it means that the last item added to the stack will be the first item to be removed.

Declaration

Stack<Obj> stack=new Stack<Obj>();

Functionalities

Stack is based on two functions (methods)-

push(element)

It adds "element" to the top of the stack.

For example: If we have 1, 3, 5 in stack, and we call push(9),

9 will be added to last index of stack -> 1, 3, 5 , 9.

peek() or top()

It returns element at the top of the stack.

For example: If we have 1, 3, 5 in stack, and we call peek(),

5 will be returned (without removing it from the stack).

pop()

It removes the last element (i.e. top of stack) from stack.

For example: If we have 1, 3, 5 , 9 in stack, and we call pop(),

the function will return 9 and the stack will change to 1, 3, 5.

Real Life Applications

  • Undo mechanisms: Many software applications use stacks to implement an "undo" feature.

  • Browser history: The "back" button in a web browser is implemented using a stack, allowing users to navigate through previously visited pages.

  • Function calls and recursion: The computer's call stack keeps track of function calls, allowing programs to remember where to return after a function finishes execution.

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