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Commit 80ecbe0

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Move linked list traversals into separate section.
1 parent 2feec48 commit 80ecbe0

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9 files changed

+147
-60
lines changed

9 files changed

+147
-60
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‎README.md

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@@ -109,6 +109,9 @@ a set of rules that precisely define a sequence of operations.
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* `B` [Shellsort](src/algorithms/sorting/shell-sort)
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* `B` [Counting Sort](src/algorithms/sorting/counting-sort)
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* `B` [Radix Sort](src/algorithms/sorting/radix-sort)
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* **Linked Lists**
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* `B` [Straight Traversal](src/algorithms/linked-list/traversal)
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* `B` [Reverse Traversal](src/algorithms/linked-list/reverse-traversal)
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* **Trees**
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* `B` [Depth-First Search](src/algorithms/tree/depth-first-search) (DFS)
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* `B` [Breadth-First Search](src/algorithms/tree/breadth-first-search) (BFS)
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# Reversed Linked List Traversal
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The task is to traverse the given linked list in reversed order.
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For example for the following linked list:
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![](https://upload.wikimedia.org/wikipedia/commons/6/6d/Singly-linked-list.svg)
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The order of traversal should be:
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```text
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37 → 99 → 12
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```
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The time complexity is `O(n)` because we visit every node only once.
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## Reference
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- [Wikipedia](https://en.wikipedia.org/wiki/Linked_list)
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import LinkedList from '../../../../data-structures/linked-list/LinkedList';
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import reverseTraversal from '../reverseTraversal';
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describe('reverseTraversal', () => {
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it('should traverse linked list in reverse order', () => {
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const linkedList = new LinkedList();
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linkedList
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.append(1)
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.append(2)
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.append(3);
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const traversedNodeValues = [];
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const traversalCallback = (nodeValue) => {
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traversedNodeValues.push(nodeValue);
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};
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reverseTraversal(linkedList, traversalCallback);
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expect(traversedNodeValues).toEqual([3, 2, 1]);
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});
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});
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// it('should reverse traversal the linked list with callback', () => {
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// const linkedList = new LinkedList();
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//
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// linkedList
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// .append(1)
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// .append(2)
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// .append(3);
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//
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// expect(linkedList.toString()).toBe('1,2,3');
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// expect(linkedList.reverseTraversal(linkedList.head, value => value * 2)).toEqual([6, 4, 2]);
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// expect(() => linkedList.reverseTraversal(linkedList.head)).toThrow();
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// });
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/**
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* Traversal callback function.
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* @callback traversalCallback
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* @param {*} nodeValue
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*/
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/**
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* @param {LinkedListNode} node
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* @param {traversalCallback} callback
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*/
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function reverseTraversalRecursive(node, callback) {
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if (node) {
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reverseTraversalRecursive(node.next, callback);
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callback(node.value);
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}
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}
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/**
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* @param {LinkedList} linkedList
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* @param {traversalCallback} callback
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*/
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export default function reverseTraversal(linkedList, callback) {
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reverseTraversalRecursive(linkedList.head, callback);
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}
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# Linked List Traversal
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The task is to traverse the given linked list in straight order.
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For example for the following linked list:
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![](https://upload.wikimedia.org/wikipedia/commons/6/6d/Singly-linked-list.svg)
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The order of traversal should be:
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```text
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12 → 99 → 37
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```
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The time complexity is `O(n)` because we visit every node only once.
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## Reference
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- [Wikipedia](https://en.wikipedia.org/wiki/Linked_list)
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import LinkedList from '../../../../data-structures/linked-list/LinkedList';
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import traversal from '../traversal';
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describe('traversal', () => {
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it('should traverse linked list', () => {
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const linkedList = new LinkedList();
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linkedList
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.append(1)
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.append(2)
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.append(3);
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const traversedNodeValues = [];
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const traversalCallback = (nodeValue) => {
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traversedNodeValues.push(nodeValue);
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};
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traversal(linkedList, traversalCallback);
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expect(traversedNodeValues).toEqual([1, 2, 3]);
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});
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});
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/**
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* Traversal callback function.
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* @callback traversalCallback
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* @param {*} nodeValue
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*/
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/**
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* @param {LinkedList} linkedList
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* @param {traversalCallback} callback
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*/
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export default function traversal(linkedList, callback) {
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let currentNode = linkedList.head;
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while (currentNode) {
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callback(currentNode.value);
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currentNode = currentNode.next;
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}
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}

‎src/data-structures/linked-list/LinkedList.js

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@@ -208,40 +208,6 @@ export default class LinkedList {
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return this.toArray().map(node => node.toString(callback)).toString();
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}
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/**
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* Traverse through all nodes of the list from head to tail
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* @param {*} callback
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* @return {LinkedListNode[]}
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*/
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traverse(callback = undefined) {
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if (typeof callback !== 'function') {
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throw new TypeError(`traverse method requires a callback function as an argument.\nArgument given: ${typeof callback}`);
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}
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let currentNode = this.head;
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const traversedNodes = [];
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while (currentNode) {
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traversedNodes.push(callback(currentNode.value));
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currentNode = currentNode.next;
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}
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return traversedNodes;
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}
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/**
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* The items in the list have been traversed in reverse order
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*/
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reverseTraversal(node, callback = undefined) {
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if (typeof callback !== 'function') {
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throw new TypeError(`reverseTraverse method requires a callback function as an argument.\nArgument given: ${typeof callback}`);
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}
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if (!node) return [];
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return this.reverseTraversal(node.next, callback).concat(callback(node.value));
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}
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/**
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* Reverse a linked list.
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* @returns {LinkedList}

‎src/data-structures/linked-list/__test__/LinkedList.test.js

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@@ -218,31 +218,6 @@ describe('LinkedList', () => {
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expect(linkedList.find({ value: 2, customValue: 'test5' })).toBeNull();
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});
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it('should traverse through all nodes of the list from head to tail with callback', () => {
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const linkedList = new LinkedList();
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linkedList
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.append(1)
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.append(2)
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.append(3);
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expect(linkedList.traverse(value => value * 2)).toEqual([2, 4, 6]);
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expect(() => linkedList.traverse()).toThrow();
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});
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it('should reverse traversal the linked list with callback', () => {
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const linkedList = new LinkedList();
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linkedList
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.append(1)
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.append(2)
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.append(3);
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expect(linkedList.toString()).toBe('1,2,3');
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expect(linkedList.reverseTraversal(linkedList.head, value => value * 2)).toEqual([6, 4, 2]);
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expect(() => linkedList.reverseTraversal(linkedList.head)).toThrow();
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});
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it('should reverse linked list', () => {
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const linkedList = new LinkedList();
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// Reverse linked list.
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linkedList.reverse();
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expect(linkedList.toString()).toBe('3,2,1');
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expect(linkedList.head.value).toBe(3);
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expect(linkedList.tail.value).toBe(1);
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// Reverse linked list back to initial state.
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linkedList.reverse();
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expect(linkedList.toString()).toBe('1,2,3');
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expect(linkedList.head.value).toBe(1);
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expect(linkedList.tail.value).toBe(3);
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});
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});

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