Implement Linked List Operations - Implement Linked List Operations

JavaScript
1

Tell us what’s happening:

  1. clear should remove all elements from the list.

Your code so far

// Node constructor
function Node(value) {
  this.value = value;
  this.next = null;
}

// 1. initList
function initList() {
  return {
    head: null,
    length: 0
  };
}

// 2. add
function add(list, element) {
  const newNode = new Node(element);

  if (!list.head) {
    list.head = newNode;
  } else {
    let current = list.head;
    while (current.next) {
      current = current.next;
    }
    current.next = newNode;
  }

  list.length++;
}

// 3. remove (fixed)
function remove(list, element) {
  if (!list.head) return;

  let current = list.head;
  let previous = null;

  while (current) {
    if (current.value === element) {
      if (previous === null) {
        list.head = current.next;
      } else {
        previous.next = current.next;
      }

      list.length--; // ✅ always decrease
      return;
    }

    previous = current;
    current = current.next;
  }
}

// 4. contains
function contains(list, element) {
  let current = list.head;

  while (current) {
    if (current.value === element) return true;
    current = current.next;
  }

  return false;
}

// 5. getAt
function getAt(list, index) {
  if (index < 0 || index >= list.length) return undefined;

  let current = list.head;
  let i = 0;

  while (i < index) {
    current = current.next;
    i++;
  }

  return current.value;
}

// 6. insertAt
function insertAt(list, index, element) {
  if (index < 0 || index > list.length) return;

  const newNode = new Node(element);

  if (index === 0) {
    newNode.next = list.head;
    list.head = newNode;
    list.length++;
    return;
  }

  let current = list.head;
  let i = 0;

  while (i < index - 1) {
    current = current.next;
    i++;
  }

  newNode.next = current.next;
  current.next = newNode;

  list.length++;
}

// 7. removeAt (fixed)
function removeAt(list, index) {
  if (index < 0 || index >= list.length) return;

  // ✅ explicit single element case
  if (list.length === 1 && index === 0) {
    list.head = null;
    list.length = 0;
    return;
  }

  // remove first
  if (index === 0) {
    list.head = list.head.next;
    list.length--;
    return;
  }

  let current = list.head;
  let i = 0;

  while (i < index - 1) {
    current = current.next;
    i++;
  }

  current.next = current.next.next;
  list.length--;
}

// 8. clear (fixed)
function clear(list) {
  list.head = null;
  list.length = 0;
}

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Challenge Information:

Implement Linked List Operations - Implement Linked List Operations

2

Please Tell us what’s happening in your own words.

Learning to describe problems is hard, but it is an important part of learning how to code.

Also, the more you say, the more we can help!

3

I’m building a linked list with functions like add, remove, removeAt, and clear. Most functions work, but the tests for remove, removeAt, and clear fail sometimes.

remove should decrease the length by one, but I’m not sure if it handles all edge cases.
removeAt should reset the list when removing the only element, and handle first/last elements correctly.
clear sets head = null and length = 0, but the test still fails.

I think the issue is with edge cases like single-node lists, last-node removal, or invalid indices. I need advice on fixing these functions so all tests pass.

4

I have pass all the steps. thanks fir your advise on describing my problem.

1 Like