ds-algo-study/DS-n-Algos/Fifo-Lifo/stack_queue_interview_problems/lib/2_min_max_stack.js

Just experimenting with publishing a package

// ============================================================================
// Interview Problem: Constant Time Stack Max
// ============================================================================
//
// -------
// Prompt:
// -------
//
// Modify the definition of the Stack class provided to create an enhanced
// version of a Stack data structure called MinMaxStack.
//
// A MinMaxStack has all of the same behavior as a Stack, but can also return
// the node with the minimum or maximum value in constant time.
//
// You may alter any of the original Stack's methods, including the
// constructor.
//
// Values of nodes of the MinMaxStack are always guaranteed to be numbers.
//
//
// ------------
// Constraints:
// ------------
//
// (1) All MinMaxStack methods must run in constant time, O(1).
//
//
// --------
// Example:
// --------
//
// const minMaxStack = new MinMaxStack();
//
// minMaxStack.push(10);
// minMaxStack.push(12);
// minMaxStack.push(8);
// minMaxStack.push(2);
// minMaxStack.push(20);
//
// console.log(minMaxStack.min().value);   => 2
// console.log(minMaxStack.max().value);   => 20
//
// minMaxStack.pop();
// console.log(minMaxStack.min().value);   => 2
// console.log(minMaxStack.max().value);   => 12
//
// minMaxStack.pop();
// console.log(minMaxStack.min().value);   => 8
// console.log(minMaxStack.max().value);   => 12
//
// minMaxStack.pop();
// console.log(minMaxStack.min().value);   => 10
// console.log(minMaxStack.max().value);   => 12
//
// minMaxStack.pop();
// console.log(minMaxStack.min().value);   => 10
// console.log(minMaxStack.max().value);   => 10
//
// minMaxStack.pop();
// console.log(minMaxStack.min());   => null
// console.log(minMaxStack.max());   => null
//
//
// -----------
// Let's code!
// -----------
class Node {
	constructor(val) {
		this.value = val;
		this.next = null;
	}
}

// Refactor the regular Stack below into a MinMaxStack!
class MinMaxStack {
	constructor() {
		this.top = null;
		this.bottom = null;
		this.length = 0;
		this.minValueNodes = [];
		this.maxValueNodes = [];
	}

	push(val) {
		const newNode = new Node(val);
		if (!this.top) {
			this.top = newNode;
			this.bottom = newNode;
		} else {
			const temp = this.top;
			this.top = newNode;
			this.top.next = temp;
		}

		if (!this.minValueNodes.length || val < this.minValueNodes[this.minValueNodes.length - 1].value)
			this.minValueNodes.push(newNode);
		if (!this.maxValueNodes.length || val > this.maxValueNodes[this.maxValueNodes.length - 1].value)
			this.maxValueNodes.push(newNode);

		return ++this.length;
	}

	pop() {
		if (!this.top) {
			return null;
		}
		const temp = this.top;
		if (this.top === this.bottom) {
			this.bottom = null;
		}
		if (this.top === this.minValueNodes[this.minValueNodes.length - 1]) this.minValueNodes.pop();
		if (this.top === this.maxValueNodes[this.maxValueNodes.length - 1]) this.maxValueNodes.pop();
		this.top = this.top.next;
		this.length--;
		return temp;
	}

	size() {
		return this.length;
	}

	min() {
		return this.minValueNodes[this.minValueNodes.length - 1] || null;
	}

	max() {
		return this.maxValueNodes[this.maxValueNodes.length - 1] || null;
	}
}

// Forgetting something down here?
exports.Node = Node;
exports.MinMaxStack = MinMaxStack;