19. Singly Linked Lists.js

// SINGLY LINKED LISTS
// É uma lista que não possui índices e os elementos são ligados um ao outro em uma direção apenas.
// É como uma escadaria de um prédio, não é possível pegar elevador e ir direto ao andar(elemento) que se quer sem que se passe por todos os anteriores.
// 

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

class SinglyLinkedList {
    constructor() {
        this.head = null;
        this.tail = null;
        this.length = 0;
    }
    push(val) {
        var newNode = new Node(val);
        if (!this.head) {
            this.head = newNode;
            this.tail = newNode;
        } else {
            this.tail.next = newNode;
            this.tail = newNode;
        }
        this.length++;
        return this;
    }
    pop() {
        if (!this.head) return undefined;
        var current = this.head;
        var newTail = current;
        while (current.next) {
            newTail = current;
            current = current.next;
        }
        this.tail = newTail;
        this.tail.next = null;
        this.length--;
        if (this.length === 0) {
            this.head = null;
            this.tail = null;
        }
        return current;
    }
    shift() {
        if (!this.head) return undefined;
        var currentHead = this.head;
        this.head = currentHead.next;
        this.length--;
        if (this.length === 0) {
            this.tail = null;
        }
        return currentHead;
    }
    unshift(val) {
        var newNode = new Node(val);
        if (!this.head) {
            this.head = newNode;
            this.tail = this.head;
        }
        newNode.next = this.head;
        this.head = newNode;
        this.length++;
        return this;
    }
    get(index) {
        if (index < 0 || index >= this.length) return null;
        var counter = 0;
        var current = this.head;
        while (counter !== index) {
            current = current.next;
            counter++;
        }
        return current;
    }
    set(index, val) {
        var foundNode = this.get(index);
        if (foundNode) {
            foundNode.val = val;
            return true;
        }
        return false;
    }
    insert(index, val) {
        if (index < 0 || index > this.length) return false;
        if (index === this.length) return !!this.push(val);
        if (index === 0) return !!this.unshift(val);

        var newNode = new Node(val);
        var prev = this.get(index - 1);
        var temp = prev.next;
        prev.next = newNode;
        newNode.next = temp;
        this.length++;
        return true;
    }
    remove(index) {
        if (index < 0 || index >= this.length) return undefined;
        if (index === 0) return this.shift();
        if (index === this.length - 1) return this.pop();
        
        var previousNode = this.get(index - 1);
        var removed = previousNode.next;
        previousNode.next = removed.next;
        this.length--;
        return removed;
    }
    reverse() {
        var node = this.head;
        this.head = this.tail;
        this.tail = node;
        var next;
        var prev = null;
        for (var i = 0; i < this.length; i++) {
            next = node.next;
            node.next = prev;
            prev = node;
            node = next;
        }
        return this;
    }
    print() {
        var arr = [];
        var current = this.head
        while (current) {
            arr.push(current.val)
            current = current.next
        }
        console.log(arr);
    }
}

var list = new SinglyLinkedList()

list.push(100)