Sort a Stack using Temp Stack

sort-stack-using-temp-stack.js

class Node {
    constructor(val) {
        this.val = val;
        this.next = null;

    }
}

class Stack {
    constructor() {
        this.first = null;
        this.last = null;
    }

    push(val) {
        let newNode = new Node(val);

        if(this.first === null) {
            this.first = newNode;
            this.last = newNode;
        } else{
            newNode.next = this.first;
            this.first = newNode;
        }

        return this.first;
    }

    pop() {
        if (this.first === null) return null;

        let temp = this.first;

        if (this.first === this.last) {
            this.last = null;
        }

        this.first = this.first.next;

        return temp;
    }

    peek() {
        return this.first;
    }

}

function sortStack(mainStack, tempStack) {

    
    let firstNode = mainStack.pop();
    tempStack.push(firstNode.val);

    while(mainStack.first !== null) {
        let tempNode = mainStack.pop();


        while(tempStack.first !== null) {
            if(tempNode.val < tempStack.peek().val) {
                let poppedNode = tempStack.pop();
                mainStack.push(poppedNode.val);
            } else{
                break;
            }
        }

        tempStack.push(tempNode.val)
    }

    while(tempStack.first !== null) {
       let currentNode = tempStack.pop();
       mainStack.push(currentNode.val)
    }

    return mainStack;
}

let itemStack = new Stack();

itemStack.push(1);
itemStack.push(2);
itemStack.push(3);

let tempStack = new Stack();

let sortedStack = sortStack(itemStack, tempStack);
console.log(sortedStack)