stack

Stack

Description

A stack is a data structure that can store and retrieve one item at a time, in last-in-first-out (LIFO) order. Imagine stacking plates on top of each other or grabbing them from the top one at a time. When you want a plate, you grab one from the top, and when you are done using it, you put it back on the top.

Stack implements LIFO through two operations: push and pop, which can be visualized in the diagram below:

(A stack is usually visualized from bottom-to-top)

• push operation stores the item at the top of the stack.
• pop operation retrieves the item from the top of the stack.

Implementation

In this exercise, implement the following functions for the Stack class

• isEmpty()
  • Write a method that returns true if the stack is currently empty.
• peek()
  • Write a method that returns the element from the top of the stack.
• push(el)
  • Write a method that stores an element(el) into the stack.
• pop()
  • Write a method that retrieves an element from the stack.
• toString()
  • The stringify method has been provided for you.

Stack Exercises

Bracket Matching

Write an algorithm to determine if all of the delimiters in an expression are matched and closed.

• Delimiters are ( { [
  • Closed is () and (() would not be closed
  • Matched is {}, and {] would not be matched.

const bracketMatch = string => {

}

console.log(bracketMatch('{ac[bb]}') === true);
console.log(bracketMatch('[dklf(df(kl))d]{}') === true);
console.log(bracketMatch('{[[[]]]}') === true);
console.log(bracketMatch('{3234[fd') === false);
console.log(bracketMatch('{df][d}') === false);
console.log(bracketMatch('([)]') === false);