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Q11. What is the difference between pop and peek function of stack ?

Ans. pop method pulls the top element from the stack and then move the top to the next element whereas peek only get the top element but doesn't move the top.

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Q12. What is the difference between Data Type and Data Structure ?

Ans. Data type: a set of values together with operations on that type
Data structure: a physical implementation of a data type

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Q13. Do you see Class as a Data Type or Data Structure ?

Ans. Class can be better seen as Data Type. This could be implemented as a Data Structure too in some cases.

One thing worth understanding here is that Data type and Data structure are conceptual things. Class could be implementation of either of these.

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Q14. How to determine if the linked list has a cycle in it ?

Ans. http://stackoverflow.com/questions/494830/how-to-determine-if-a-linked-list-has-a-cycle-using-only-two-memory-locations

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Q15. Which Data Structure should be used for Load Balancer ?

Ans. [ Open Ended question ]

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Q16. Explain what happens when insertion is performed in case of ArrayList and LinkedList.

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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Q17. What is the difference between circular queue and priority queue ?

Data Structures

Ans. https://qr.ae/TWK2Ok

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Q18. Write program to create a linked list and perform different operations on it.

Ans. import java.util.*;
class LinkedListSolution{
protected LinkedList list;
public LinkedListSolution(){
list = new LinkedList();
}
public Object pop() throws NoSuchElementException{
if(list.isEmpty())
throw new NoSuchElementException();
else
return list.removeFirst();
}
public void push(Object obj){
list.addFirst(obj);
}
public Object peek() throws NoSuchElementException{
if(list.isEmpty())
throw new NoSuchElementException();
else
return list.getFirst();
}
public boolean isEmpty(){
return list.isEmpty();
}
public String toString(){
return list.toString();
}
}
class TestStack{
public static void main(String args[]){
LinkedListSolution s = new LinkedListSolution();
s.push("First");
s.push("Second");
s.push("Third");
System.out.println("Top: " s.peek());
s.push("Fourth");
while(!(s.isEmpty()))
System.out.println(s.pop());
}
}

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Q19. Write a Program to delete a node from Linked List ?

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Q20. What data structure will you use if we have to search an element in million of elements ?

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Q21. Write a Program to find the middle element of Linked List ?

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Q22. Write a Program to merge two sorted arrays ?

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

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Q23. Implement stack using generics in Java.

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Q24. How to implement a hashtable ?

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Q25. 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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Q26. Difference between Tree and Graph ?

Data Structures

Ans. Graph contain cycles whereas Trees cannot.

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Q27. Write a Program to implement stack using LinkedList.

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Q28. Describe how you could use a single array to implement three stacks

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Q29. Write a program to sort a stack in ascending order You should not make any assumptions about how the stack is implemented The following are the only functions that should be used to write this program: push | pop | peek | isEmpty

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Q30. In a Tree, find common ancestor of two nodes.

Data Structures

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Q31. Which Data structure can be used for creating Queue ?

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Q32. Which of the two - Arrays or LinkedList - is a better data structure for implementing Queue ? and Why ?

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Q33. Write a program for binary tree ?

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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Q34. Write an efficient program for printing k largest elements in an array. Elements in array can be in any order.

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Q35. What are the ways to get the values from list ?

Ans. list.get(index);

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Q36. Find Max from Stack in O(1) complexity

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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Q37. How would you implement low latency data structures ?

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Q38. Create a stack of specific size using arrayList?

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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Q39. How are hash codes generated ?

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

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Q40. Difference between Arrays and LinkedList ?

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