What is the best way to practice solving linked list problems from LeetCode on your personal computer?

Question

What is the best way to practice solving linked list problems from LeetCode on your personal computer?

Is there a way to execute the linked list programs on my local machine? I am able to run this code in their input field, but I'm having trouble running it on my local machine.

  function ListNode(val, next) {
      this.val = (val===undefined ? 0 : val)
      this.next = (next===undefined ? null : next)
  }
 
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */

var mergeTwoLists = function (l1, l2) {
  var mergedHead = { val: -1, next: null },
    crt = mergedHead;
  while (l1 && l2) {
    if (l1.val > l2.val) {
      crt.next = l2;
      l2 = l2.next;
    } else {
      crt.next = l1;
      l1 = l1.next;
    }
    crt = crt.next;
  }
  crt.next = l1 || l2;
  return mergedHead.next;
};

mergeTwoLists([1, 2, 4], [1, 3, 4]);

javascript linked-list

Answer 1

Answer №1

If you want to convert an array to a linked list and vice versa, you can make use of these handy helper functions. They essentially perform the same task as the LeetCode framework does in the background.

const convertArrayToList = arr => arr.length ? new ListNode(arr[0], convertArrayToList(arr.slice(1)))  
                                    : null;
const convertListToArray = head => head ? [head.val].concat(convertListToArray(head.next)) 
                                   : [];

Here's an example of how you can utilize these functions:

const convertedArray = convertListToArray(
    mergeTwoLists(convertArrayToList([1, 2, 4]), convertArrayToList([1, 3, 4]))
);

Answer 2

If you want to convert an array to a linked list and vice versa, you can make use of these handy helper functions. They essentially perform the same task as the LeetCode framework does in the background.

const convertArrayToList = arr => arr.length ? new ListNode(arr[0], convertArrayToList(arr.slice(1)))  
                                    : null;
const convertListToArray = head => head ? [head.val].concat(convertListToArray(head.next)) 
                                   : [];

Here's an example of how you can utilize these functions:

const convertedArray = convertListToArray(
    mergeTwoLists(convertArrayToList([1, 2, 4]), convertArrayToList([1, 3, 4]))
);

Answer 3

Answer №2

After creating custom ListNode and LinkedList classes, I successfully ran the mergeTwoLists method locally. The code snippet below showcases how the runCase function merges two ListNodes (heads of linked lists) and prints the result. To generate a linked list from LeetCode test case inputs, we can use the toArray method and convert the result back to an array using the fromArray function available in the LinkedList class.

class ListNode {
  constructor(val=0, next=null) {
      this.val = val;
      this.next = next;             
  }
}

class LinkedList {
  constructor(head = null) {
    this.head = head
  }

  static fromArray(array) {
    const linkedList = new LinkedList();

    for (let i = array.length - 1; i >= 0; i--) {
      const node = new ListNode(array[i]);
      node.next = linkedList.head;
      linkedList.head = node;
    }

    return linkedList;
  }

  toArray() {
    const array = [];
    let current = this.head;

    while (current) {
      array.push(current.val);
      current = current.next;
    }

    return array;
  }
}

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 *
 * @param {ListNode} node1
 * @param {ListNode} node2
 * @return {ListNode}
 */
var mergeTwoLists = function(node1, node2) {
  let loco = new ListNode();
  let current = loco;

  while (node1 && node2) {
    if (node1.val > node2.val) {
      current.next = node2;
      node2 = node2.next;
    } else {
      current.next = node1;
      node1 = node1.next;
    }
    current = current.next;
  }
  current.next = node1 || node2;

  return loco.next;
};

const runCase = (array1, array2) => {
  const node1 = LinkedList.fromArray(array1).head;
  const node2 = LinkedList.fromArray(array2).head;

  const result = mergeTwoLists(node1, node2);
  const linkedList = new LinkedList(result);
  console.log(linkedList.toArray());
}

runCase([1, 2, 4], [1, 3, 4]); // [1,1,2,3,4,4]
runCase([], []); // []
runCase([], [0]); // [0]

Reference

21. Merge Two Sorted Lists by LeetCode
How to Implement a Linked List in JavaScript by Sarah Chima Atuonwu

Answer 4

After creating custom ListNode and LinkedList classes, I successfully ran the mergeTwoLists method locally. The code snippet below showcases how the runCase function merges two ListNodes (heads of linked lists) and prints the result. To generate a linked list from LeetCode test case inputs, we can use the toArray method and convert the result back to an array using the fromArray function available in the LinkedList class.

class ListNode {
  constructor(val=0, next=null) {
      this.val = val;
      this.next = next;             
  }
}

class LinkedList {
  constructor(head = null) {
    this.head = head
  }

  static fromArray(array) {
    const linkedList = new LinkedList();

    for (let i = array.length - 1; i >= 0; i--) {
      const node = new ListNode(array[i]);
      node.next = linkedList.head;
      linkedList.head = node;
    }

    return linkedList;
  }

  toArray() {
    const array = [];
    let current = this.head;

    while (current) {
      array.push(current.val);
      current = current.next;
    }

    return array;
  }
}

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 *
 * @param {ListNode} node1
 * @param {ListNode} node2
 * @return {ListNode}
 */
var mergeTwoLists = function(node1, node2) {
  let loco = new ListNode();
  let current = loco;

  while (node1 && node2) {
    if (node1.val > node2.val) {
      current.next = node2;
      node2 = node2.next;
    } else {
      current.next = node1;
      node1 = node1.next;
    }
    current = current.next;
  }
  current.next = node1 || node2;

  return loco.next;
};

const runCase = (array1, array2) => {
  const node1 = LinkedList.fromArray(array1).head;
  const node2 = LinkedList.fromArray(array2).head;

  const result = mergeTwoLists(node1, node2);
  const linkedList = new LinkedList(result);
  console.log(linkedList.toArray());
}

runCase([1, 2, 4], [1, 3, 4]); // [1,1,2,3,4,4]
runCase([], []); // []
runCase([], [0]); // [0]

Reference

21. Merge Two Sorted Lists by LeetCode
How to Implement a Linked List in JavaScript by Sarah Chima Atuonwu

What is the best way to practice solving linked list problems from LeetCode on your personal computer?

Answer №1

Answer №2

Reference

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