Mock Interview Questions

What is a linked list and how does it differ from an array?

What are the types of linked lists?

What is the time complexity of inserting a node at the beginning of a linked list?

What is the time complexity of deleting a node from a linked list?

How do you implement a stack using a linked list?

How do you implement a queue using a linked list?

What is the advantage of using a linked list over an array?

What is the disadvantage of using a linked list?

How do you handle memory allocation and deallocation in a linked list?

What is the purpose of the 'next' pointer in a linked list node?

What is the purpose of the 'prev' pointer in a doubly linked list node?

How do you detect a cycle in a linked list?

What is the time complexity of finding the middle node of a linked list?

How do you reverse a linked list?

What is the purpose of a sentinel node in a linked list?

How do you implement a hash table using a linked list?

What is the advantage of using a doubly linked list over a singly linked list?

What is the disadvantage of using a doubly linked list?

How do you handle node deletion in a doubly linked list?

What is the purpose of a 'dummy' node in a linked list?

Write a function to insert a node at the beginning of a linked list

function insertAtBeginning(head, data) {
  var newNode = new Node(data);
  newNode.next = head;
  head = newNode;
  return head;
}

Write a function to delete a node from a linked list

function deleteNode(head, data) {
  if (head == null) return null;
  if (head.data == data) {
    head = head.next;
    return head;
  }
  var current = head;
  while (current.next != null) {
    if (current.next.data == data) {
      current.next = current.next.next;
      return head;
    }
    current = current.next;
  }
  return head;
}

Write a function to find the middle node of a linked list

function findMiddleNode(head) {
  var slow = head;
  var fast = head;
  while (fast != null && fast.next != null) {
    slow = slow.next;
    fast = fast.next.next;
  }
  return slow;
}

Write a function to reverse a linked list

function reverseList(head) {
  var prev = null;
  var current = head;
  while (current != null) {
    var next = current.next;
    current.next = prev;
    prev = current;
    current = next;
  }
  return prev;
}

Write a function to detect a cycle in a linked list

function detectCycle(head) {
  var slow = head;
  var fast = head;
  while (fast != null && fast.next != null) {
    slow = slow.next;
    fast = fast.next.next;
    if (slow == fast) return true;
  }
  return false;
}

Write a function to find the nth node from the end of a linked list

function findNthNodeFromEnd(head, n) {
  var length = 0;
  var current = head;
  while (current != null) {
    length++;
    current = current.next;
  }
  current = head;
  for (var i = 0; i < length - n; i++) {
    current = current.next;
  }
  return current;
}

Write a function to merge two sorted linked lists

function mergeLists(list1, list2) {
  var dummy = new Node(0);
  var current = dummy;
  while (list1 != null && list2 != null) {
    if (list1.data < list2.data) {
      current.next = list1;
      list1 = list1.next;
    } else {
      current.next = list2;
      list2 = list2.next;
    }
    current = current.next;
  }
  if (list1 != null) {
    current.next = list1;
  } else {
    current.next = list2;
  }
  return dummy.next;
}

Write a function to find the first node of the loop in a linked list

function findFirstNodeOfLoop(head) {
  var slow = head;
  var fast = head;
  while (fast != null && fast.next != null) {
    slow = slow.next;
    fast = fast.next.next;
    if (slow == fast) break;
  }
  if (slow != fast) return null;
  slow = head;
  while (slow != fast) {
    slow = slow.next;
    fast = fast.next;
  }
  return slow;
}

Write a function to find the node where the cycle begins in a linked list

function findCycleBeginNode(head) {
  var slow = head;
  var fast = head;
  while (fast != null && fast.next != null) {
    slow = slow.next;
    fast = fast.next.next;
    if (slow == fast) break;
  }
  if (slow != fast) return null;
  slow = head;
  while (slow != fast) {
    slow = slow.next;
    fast = fast.next;
  }
  return slow;
}

Write a function to find the length of a linked list

function findLength(head) {
  var length = 0;
  var current = head;
  while (current != null) {
    length++;
    current = current.next;
  }
  return length;
}