DynamicLinkedList.js

/*

A singly linked list is collection of nodes wherein each node has 2 parts: data and a pointer to the next node. 
The list terminates with a node pointing at null. Below is the program to add nodes dynamically in Singly Linked List.

In this program, user can provide a choice to perform operations on a Singly Linked List. It is created using a ES6 class syntax. 
prompt & colors are node packages for taking user input and displaying text in different colors respectively. 

*/

const prompt = require("prompt-sync")({ sigint: true });
const colors = require("colors");

// Setting the Color schema
colors.setTheme({
  display: "green",
  insert: "white",
  delete: "red",
  leave: "yellow",
  end: "rainbow",
  wrong: "america",
});

// Creating the node class to create nodes
class Node {
  constructor(value, next = null) {
    this.value = value;
    this.next = next;
  }
}

// Creating Linked List class to perform operations
class LinkedList {
  constructor(value) {
    this.head = {
      value: value,
      next: null,
    };

    this.tail = this.head;
    this.length = 1;
  }

  // Looping to a given index in Linked List
  traverseToIndex(index) {
    let counter = 1;
    let currentNode = this.head;

    while (counter !== index) {
      currentNode = currentNode.next;
      counter++;
    }

    return currentNode;
  }

  // Appending (at the end) node in linked list
  append(value) {
    const newNode = new Node(value);

    this.tail.next = newNode;
    this.tail = newNode;
    this.length++;

    return this;
  }

  // Prepending ( at the beginning ) of linked list
  prepend(value) {
    const newNode = new Node(value);

    newNode.next = this.head;
    this.head = newNode;
    this.length++;

    return this;
  }

  // Inserting node at a given position in linked list
  insert(index, value) {
    if (index === 1) return this.prepend(value);
    else if (index > this.length) return this.append(value);
    else {
      const newNode = new Node(value);
      let currentNode = this.traverseToIndex(index - 1);

      newNode.next = currentNode.next;
      currentNode.next = newNode;
      this.length++;
    }
  }

  // Removing the element node form linked list
  remove(index) {
    if (index === 1) {
      this.head = this.head.next;
      this.length--;
      return;
    }

    // Traversing to that particular node element
    let currentNode = this.traverseToIndex(index - 1);
    if (index === this.length) {
      currentNode.next = null;
      this.length--;
      return this;
    }

    currentNode.next = currentNode.next.next;
    this.length--;

    return this;
  }

  // Reverse the linked list
  reverse() {
    if (!this.head.next) {
      return this.head;
    }

    let first = this.head;
    this.tail = this.head;
    let second = first.next;

    while (second) {
      const temp = second.next;
      second.next = first;
      first = second;
      second = temp;
    }

    this.head.next = null;
    this.head = first;

    return this;
  }

  // Sort the linked list using bubble sort algorithm in ascending order
  bubbleSort() {
    let firstNode, secondNode;
    firstNode = this.head;

    while (firstNode !== null) {
      secondNode = this.head;

      while (secondNode !== null) {
        if (firstNode.value < secondNode.value) {
          let temp = secondNode.value;
          secondNode.value = firstNode.value;
          firstNode.value = temp;
        }

        secondNode = secondNode.next;
      }

      firstNode = firstNode.next;
    }

    return this;
  }

  // Get the middle node of Linked List
  getMidNode(start, last) {
    if (start === null) return null;

    let slowTraverse = start;
    let fastTraverse = start.next;

    while (fastTraverse !== last && fastTraverse.next !== null) {
      fastTraverse = fastTraverse.next.next;
      slowTraverse = slowTraverse.next;
    }

    return slowTraverse;
  }

  // Start point for performing the merge sort
  setMergeSort() {
    // Call the mergesort algorithm and set the result to head 
    let head = this.mergeSort(this.head)
    
    // to update the tail of returned linked list i.e head here
    let setTail = head
    while(setTail.next !== null) setTail = setTail.next

    return this.tail = setTail
  }

  // Perform the merge sort
  mergeSort(linkedList) {
    // set start and last of linked list
    let start = linkedList;
    let last = null;
    if (start.next === null) return start;

    // get the middle node
    let middle = this.getMidNode(start, last);
    let middleNext = middle.next;
    middle.next = null;

    // create two halved of linked list
    let rightPart = middleNext;
    let leftPart = start;

    // pass the respective halves to comapre the elements  
    this.head = this.mergeLL(
      this.mergeSort(leftPart),
      this.mergeSort(rightPart)
    );

    return this.head
  }

  // Perform comparison of two different linked lists
  mergeLL(left, right) {
    let sorted;

    if (left === null) return right;
    if (right === null) return left;

    // check elements & add it to the new linked list
    if (left.value < right.value) {
      sorted = new Node(left.value);
      sorted.next = this.mergeLL(left.next, right);
    } else {
      sorted = new Node(right.value);
      sorted.next = this.mergeLL(left, right.next);
    }

    return sorted;
  }

  // Performing binary search
  binarySearch(key) {
    let startNode = this.head;
    let lastNode = null;

    do {
      let mid = this.getMidNode(startNode, lastNode);

      if (mid === null) return null;
      if (mid.value === key) return console.log("Found ", mid.value);
      else if (mid.value < key) {
        startNode = mid.next;
      } else {
        lastNode = mid;
      }
    } while (lastNode === null || lastNode !== startNode);

    return console.log("Not Found");
  }

  // Displaying all the nodes of linked list
  printList() {
    const array = [];
    let currentNode = this.head;

    while (currentNode !== null) {
      array.push(currentNode.value);
      currentNode = currentNode.next;
    }

    return array;
  }
}

// Instantiating the Linked List class
const myLinkedList = new LinkedList(10);

let choice = 0;
let value, index;

// Asking user input for performing operations on Linked List
do {
  console.log("\nWelcome to the Linked List Show");
  console.log("Follow the instructions to get in the show");
  console.log("0. To exit without doing anything".yellow);
  console.log("1. Display the Linked List".display);
  console.log("2. Append element in the Linked List".insert);
  console.log("3. Prepend element in the Linked List".insert);
  console.log("4. Insert at any position in the Linked List".insert);
  console.log("5. Delete element from Linked List".delete);
  console.log("6. Reverse a Linked List".display);
  console.log("7. Sort the Linked List using Bubble Sort".insert);
  console.log("8. Search node using binary search".display);
  console.log("9. Sort the Linked List using Merge Sort".display);


  choice = +prompt("Enter your choice - ");

  switch (choice) {
    case 0:
      console.log("Hmm, matter of choice!\n".rainbow);
      return;

    case 1:
      console.log("Linked List - ", myLinkedList.printList());
      break;

    case 2:
      value = +prompt("Enter Value to Append element - ");
      myLinkedList.append(value);
      console.log("After Append Linked List - ", myLinkedList.printList());
      break;

    case 3:
      value = +prompt("Enter Value to Prepend element - ");
      myLinkedList.prepend(value);
      console.log("After Prepend Linked List - ", myLinkedList.printList());
      break;

    case 4:
      value = +prompt("Enter Value to Insert element - ");
      index = +prompt("Enter Position to Insert element - ");

      if (index <= 0)
        return console.log("You know this is wrong, Bbye!\n".wrong);
      myLinkedList.insert(index, value);
      console.log("After Insertion Linked List - ", myLinkedList.printList());
      break;

    case 5:
      if (myLinkedList.length === 0) {
        return console.log("404, you can't remove anything from void".wrong);
      }

      index = +prompt("Enter position of element - ");
      if (index <= 0 || index > myLinkedList.length)
        return console.log("You know this is wrong, Bbye!\n".wrong);

      myLinkedList.remove(index);
      console.log("After Deletion Linked List - ", myLinkedList.printList());
      break;

    case 6:
      if (myLinkedList.length === 0) {
        return console.log("Can't revert, Empty Linked List".wrong);
      }

      myLinkedList.reverse();
      console.log("Reversal of Linked List - ", myLinkedList.printList());
      break;

    case 7:
      if (myLinkedList.length === 0) {
        console.log("Linked List is Empty");
      } else {
        myLinkedList.bubbleSort();
        console.log("After sorting Linked List - ", myLinkedList.printList());
      }

      break;

    case 8:
      value = +prompt("Enter Value to Search - ");
      // Sort the linked list
      myLinkedList.bubbleSort();

      myLinkedList.binarySearch(value);
      break;

    case 9:
      myLinkedList.setMergeSort();
      console.log("After merge sort - ", myLinkedList.printList());
      break;

    default:
      console.log("You know this is wrong, Bbye!\n".wrong);
      return;
  }
} while (choice !== 0);

// Sample I/O of the above program -

/*

Welcome to the Linked List Show
Follow the instructions to get in the show
0. To exit without doing anything
1. Display the Linked List
2. Append element in the Linked List
3. Prepend element in the Linked List
4. Insert anywhere in between the Linked List
5. Delete element from Linked List
6. Reverse a Linked List
7. Sort the Linked List using Bubble Sort
8. Search node using Binary Search
9. Sort the Linked List using Merge Sort
Enter your choice - 2
Enter Value to Append element - 43
After Append Linked List -  [10, 43]

0. To exit without doing anything
1. Display the Linked List
2. Append element in the Linked List
3. Prepend element in the Linked List
4. Insert anywhere in between the Linked List
5. Delete element from Linked List
6. Reverse a Linked List
7. Sort the Linked List using Bubble Sort
8. Search node using Binary Search
9. Sort the Linked List using Merge Sort
Enter your choice - 6
Reversal of Linked List -  [43, 10]

0. To exit without doing anything
1. Display the Linked List
2. Append element in the Linked List
3. Prepend element in the Linked List
4. Insert anywhere in between the Linked List
5. Reverse a Linked List
6. Delete element from Linked List
7. Sort the Linked List using Bubble Sort
8. Search node using Binary Search
9. Sort the Linked List using Merge Sort
Enter your choice - 7
After sorting -  [ 10, 43 ]

.... above text display
Enter your choice - 8
Enter Value to Search - 10
Found 10

- Enter few such elements using the insertion operation
... above test display
Enter your choice - 1
Linked List - [10, 43, 90, 32, 54, 21, 80]

Enter your choice - 9
After Merge Sort - [10, 21, 32, 43, 54, 80, 90]

*/