Data Structure - Interview Questions and Answers for 'Data structure' | Search Interview Question

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Q31. Write a Program to implement stack using LinkedList.

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Q32. What is the access time for ArrayList and LinkedList ?

Data Structure

Ans. O(1) for ArrayList
O(n) for LinkedList

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Q33. What is the "multiplicative congruence" method for determining where an element belongs in a hash table ?

Data Structure

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Q34. Describe how a queue is usually created using sequential allocation.

Data Structure

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Q35. If a stack is implemented using linkedlist, which end (head or tail) should represent the top ?

Data Structure

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Q36. If a stack is implemented using an array, which end (head or tail) should represent the top ?

Data Structure

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Q37. Can we access elements at a particular index using LinkedList collection class ?

Data Structure

Ans. Yes we can. But as the underlying structure of the collection class is double linked list, it will eventually have to traverse to the element linearlly and hence would result in bad performance.

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Q38. Which of the following - arrays or LinkedList allow elements to be accessed using index and how ?

Data Structure

Ans. Arrays allows elements to be accessed directly using the index.

As Array elements are stored in continuous memory locations it's very easy to find the memory address of any element using the formula as following

Memory Address of Array start or index 0 + ( Size of array element * Index )

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Q39. Difference between Arrays and LinkedList ?

Data Structure

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Q40. How are hash codes generated ?

Data Structure

Ans. Use hashCode() which returns an integer value, generated by a hashing algorithm

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Q41. Create a stack of specific size using arrayList?

Data Structure

Ans. public class StackUsingArrayList {
   public static void main(String[] args) {
      List list = new ArrayList();
      list.add("A");
      list.add("B");
      list.add("C");

      Stack stack = new Stack();

      list.forEach(a -> stack.add(a));
      System.out.println(stack);

   }
}

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Q42. How would you implement low latency data structures ?

Data Structure

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Q43. Find Max from Stack in O(1) complexity

Algorithm

Ans. Create one extra field called MAX O(1)

when you an element to the stack check these two condition
1. Stack is empty, then MAX = element
2. Stack is not empty then check if the element is greater than MAX then MAX = element

when getMax fuction is called, then return MAX

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Q44. What are the ways to get the values from list ?

Data Structure

Ans. list.get(index);

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Q45. Explain what happens when insertion is performed in case of ArrayList and LinkedList.

Data Structure

Ans. Array List works on Array and when we add an element in middle of the list, Array List need to update the index of all subsequent elements. I the capacity is full, it even may need to move the whole list to a new memory location . Linked List works on Double linked list algorithm and all it has to do is to adjust the address of the previous and next elements.

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Q46. Write an efficient program for printing k largest elements in an array. Elements in array can be in any order.

Data Structure

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Q47. Write a program for binary tree ?

Data Structure

Ans. public class BinarySearchTree {
//Represent the node of binary tree
public static class Node {
int data;
Node left;
Node right;
public Node(int data) {
//Assign data to the new node, set left and right children to null

this.data = data;
this.left = null;
this.right = null;
}
}
//Represent the root of binary tree

public Node root;
public BinarySearchTree() {
root = null;
}

//factorial() will calculate the factorial of given number

public int factorial(int num) {
int fact = 1;
if (num == 0) return 1;
else {
while (num > 1) {
fact = fact * num;
num--;
}
return fact;
}
}

//numOfBST() will calculate the total number of possible BST by calculating Catalan Number for given key

public int numOfBST(int key) {
int catalanNumber = factorial(2 * key) / (factorial(key 1) * factorial(key));
return catalanNumber;
}
public static void main(String[] args) {
BinarySearchTree bt = new BinarySearchTree();

//Display total number of possible binary search tree with key 5

System.out.println("Total number of possible Binary Search Trees with given key: "
bt.numOfBST(5));
}
}

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Q48. Which of the two - Arrays or LinkedList - is a better data structure for implementing Queue ? and Why ?

Data Structure

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Q49. Which Data structure can be used for creating Queue ?

Data Structure

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Q50. In a Tree, find common ancestor of two nodes.

Data Structures

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Q51. Write method to delete Node from a LinkedList.

Data Structure

Ans. public class LinkedList {

   Node start = null;
   Node head = null;

   class Node {
      Integer body;
      Node nextNode;

      Node(Integer value) {
         body = value;
      }
   }

   private void addNodeToEnd(Integer value) {
      if (start == null) {
         start = new Node(value);
         head = start;
         head.nextNode = null;
         return;
      }

      while (head.nextNode != null) {
         head = head.nextNode;
      }

      head.nextNode = new Node(value);
   }

   private void deleteNode(Integer value) {
      head = start;
      while (head.nextNode != null) {
         if(head.nextNode.body == value){
            head.nextNode = head.nextNode.nextNode;
         }

         head = head.nextNode;
      }
   }



   private void traverse() {
      head = start;
      while (head != null) {
         System.out.println(head.body);
         head = head.nextNode;
      }
   }

   public static void main(String[] args) {
      LinkedList ll = new LinkedList();

      ll.addNodeToEnd(5);
      ll.addNodeToEnd(10);
      ll.addNodeToEnd(15);

      ll.traverse();

      ll.deleteNode(10);

      ll.traverse();

   }
}

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Q52. In a Linked list with sorted numbers, insert a new numbers while maintaining the sort order.

Algorithm

Ans.
public class LinkedList {

   Node start = null;
   Node head = null;

   class Node{
      Integer body;
      Node nextNode;

      Node(Integer value){
         body = value;
      }
   }

   private void insertInMiddle(Integer value){
      head = start;
      if(start == null) {
         start = new Node(value);
         head = start;
         head.nextNode = null;
         return;
      }

      while(head.body < value){
         if(head.nextNode == null || head.nextNode.body >= value){
            Node newNode = new Node(value);
            newNode.nextNode = head.nextNode;
            head.nextNode = newNode;

            break;
         }
         head = head.nextNode;
      }
   }

   private void traverse(){
      head = start;
      while(head != null){
         System.out.println(head.body);
         head = head.nextNode;
      }
   }

   public static void main(String[] args){
      LinkedList ll = new LinkedList();

      ll.insertInMiddle(5);
      ll.insertInMiddle(10);
      ll.insertInMiddle(15);
      ll.insertInMiddle(7);

      ll.traverse();

   }
}

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Q53. Write a program for LinkedList, with method to append node and traversing the list ?

Algorithm

Ans. public class LinkedList {

   Node start = null;
   Node head = null;

   class Node {
      Integer body;
      Node nextNode;

      Node(Integer value) {
         body = value;
      }
   }

   private void addNodeToEnd(Integer value) {
      if (start == null) {
         start = new Node(value);
         head = start;
         head.nextNode = null;
         return;
      }

      while (head.nextNode != null) {
         head = head.nextNode;
      }

      head.nextNode = new Node(value);
   }

   private void traverse() {
      head = start;
      while (head != null) {
         System.out.println(head.body);
         head = head.nextNode;
      }
   }

   public static void main(String[] args) {
      LinkedList ll = new LinkedList();

      ll.addNodeToEnd(5);
      ll.addNodeToEnd(10);
      ll.addNodeToEnd(15);

      ll.traverse();

   }
}

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Q54. Difference between Tree and Graph ?

Data Structures

Ans. Graph contain cycles whereas Trees cannot.

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Q55. What is the difference between Stack and Queue ?

Data Structures

Ans. Stack is based on Last in First out (LIFO) principle while a queue is based on FIFO (First In First Out) principle.

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Q56. Write a Program to delete a node from Linked List ?

Data Structure

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Q57. How to implement a hashtable ?

Data Structure

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Q58. Implement stack using generics in Java.

Data Structure

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Q59. Find the third last element in a linked list ?

Data Structure

Ans. First Find the number of nodes in the linked list and take it as n.then find the data at n-3 element.

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Q60. Write a Program to merge two sorted arrays ?

Data Structure

Ans. We can merge two sorted array by using quick sort algorithm

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