Stack

by Krishna Ananthi

JavaScript

/**
 * complexity : insert, removal : O(1)
 *              search : O(n)
 */
class Node {
  constructor(value) {
    this.value = value;
    this.next = null;
  }
}

class Stack {
  constructor() {
    this.first = null;
    this.last = null;
    this.size = 0;
  }
  push(data) {
    let newNode = new Node(data);
    if (!this.first) {
      this.first = newNode;
      this.last = newNode;
    } else {
      let temp = this.first;
      this.first = newNode;
      this.first.next = temp;
    }
    this.size++;
  }
  pop() {
    let temp = this.first;
    if (this.first === this.last) {
      this.last = null;
    }
    this.first = this.first.next;
    this.size--;
  }

  peek() {
    if (!this.first) {
      return null;
    }
    let temp = this.first;
    if (this.first === this.last) {
      this.last = null;
    }
    this.first = this.first.next;
    this.size--;
    return temp.value;
  }
  printStack() {
    let temp = this.first;
    console.log(`size of stack ${this.size}`);
    while (temp != null) {
      console.log(temp.value);
      temp = temp.next;
    }
  }
}

const a = new Stack();
a.push("aa");
a.printStack();
a.push("bb");
a.printStack();
a.push("cc");
a.printStack();
console.log(a.last);