LESSON 24 / 75·2 min readIntermediate

Stack and queue in JavaScript

Should knowConcept lesson

Stack using array

const stack = [];
stack.push(1);
stack.push(2);
stack.pop();

Queue using array

const queue = [];
queue.push(1);
queue.push(2);
queue.shift();

Problems to practice

Valid Parentheses
Min Stack
Daily Temperatures
Sliding Window Maximum
Implement Queue Using Stack
Implement Stack Using Queue

Example: valid parentheses

function isValid(s) {
  const stack = [];
  const pairs = { ')': '(', ']': '[', '}': '{' };

  for (const ch of s) {
    if (['(', '[', '{'].includes(ch)) stack.push(ch);
    else {
      if (stack.pop() !== pairs[ch]) return false;
    }
  }

  return stack.length === 0;
}

PAUSE & RECALL