117 lines
2.6 KiB
JavaScript
117 lines
2.6 KiB
JavaScript
const head = Symbol("head");
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const tail = Symbol("tail");
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class DoublyLinkedListNode {
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constructor (data) {
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this.data = data;
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this.next = null;
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this.previous = null;
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}
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}
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export class DoublyLinkedList {
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constructor () {
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this[head] = null;
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this[tail] = null;
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}
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add (data) {
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const newNode = new DoublyLinkedListNode(data);
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// special case: no nodes
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if (this[head] === null) {
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this[head] = newNode;
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} else {
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// link the current tail and new tail
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this[tail].next = newNode;
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newNode.previous = this[tail];
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}
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// re-assign the tail
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this[tail] = newNode;
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}
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get (index) {
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if ( ! Number(index) < 0) {
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return undefined;
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}
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let current = this[head];
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let i = 0;
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while ((current !== null) && (i < index)) {
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current = current.next;
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i++;
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}
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return current !== null
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? current.data
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: undefined;
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}
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remove (index) {
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if ((this[head] === null) || (index < 0)) {
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throw new RangeError(`Index ${index} does not exist in the list.`);
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}
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// special case: removing the first node
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if (index === 0) {
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const data = this[head].data;
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this[head] = this[head].next;
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// Only one node
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if (this[head] === null) {
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this[tail] = null;
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} else {
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this[head].previous = null;
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}
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return data;
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}
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let current = this[head];
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let i = 0;
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while ((current !== null) && (i < index)) {
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current = current.next;
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i++;
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}
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// If node was found remove it
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if (current !== null) {
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current.previous.next = current.next;
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// last node
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if (this[tail] === current) {
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this[tail] = current.previous;
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} else {
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current.next.previous = current.previous;
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}
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return current.data;
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}
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throw new RangeError(`Index ${index} does not exist in the list.`);
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}
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*values () {
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let current = this[head];
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while (current !== null) {
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yield current.data;
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current = current.next;
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}
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}
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*reverse () {
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let current = this[tail];
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while (current !== null) {
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yield current.data;
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current = current.previous;
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}
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}
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[Symbol.iterator] () {
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return this.values();
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}
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} |