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Interview Questions and Answers for 'Algor' - 61 question(s) found - Order By Newest

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Basic and Very Frequently asked.
  Q1. What is Polymorphism in Java ?Core Java
Ans. Polymorphism means the condition of occurring in several different forms.

Polymorphism in Java is achieved in two manners

1. Static polymorphism is the polymorphic resolution identified at compile time and is achieved through function overloading whereas

2. Dynamic polymorphism is the polymorphic resolution identified at runtime and is achieved through method overriding.

  Sample Code for overloading

  Sample Code for overriding

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Advanced level question frequently asked in US based companies. Recently asked in EMC and Intuit.
  Q2. Can you provide some implementation of a Dictionary having large number of words ? Solution
Ans. Simplest implementation we can have is a List wherein we can place ordered words and hence can perform Binary Search.

Other implementation with better search performance is to use HashMap with key as first character of the word and value as a LinkedList.

Further level up, we can have linked Hashmaps like ,

hashmap {
a ( key ) -> hashmap (key-aa , value (hashmap(key-aaa,value)
b ( key ) -> hashmap (key-ba , value (hashmap(key-baa,value)
....................................................................................
z( key ) -> hashmap (key-za , value (hashmap(key-zaa,value)
}

upto n levels ( where n is the average size of the word in dictionary.

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 Q3. 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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   Like         Discuss         Correct / Improve     LinkedList  Data structures  Algorithm

 Q4. What is the difference between Graph's Breadth first and Depth First algorithm ?Algorithm
Ans. In Breadth first algorithm, all the adjacent nodes of the starting node is visited first and then the same rule is followed while moving inwards whereas

In Depth first algorithm, all the nodes of a single traversal path are visited first till a cycle or an end is found.

For example , given the following entries of adjacent nodes

1,2
1,3
1,6
2,4
2,5
3,6

The Breadth first path would be

1,2,3,6,4,5

and Depth first path would be

1,2,4,5,3,6

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   Like         Discuss         Correct / Improve     graph traversal  breadth first vs depth first        frequent

 Q5. When do you get ClassCastException?

or

What is ClassCastException ?
Ans. As we only downcast class in the hierarchy, The ClassCastException is thrown to indicate that code has attempted to cast an object to a subclass of which it is not an instance.

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 Q6. What are the pre-requisite for the collection to perform Binary Search ?
Ans. 1. Collection should have an index for random access.
2. Collection should have ordered elements.

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 Q7. Explain various Searching and Sorting Algorithms ?Algorithm
 This question was recently asked at 'HeadStrong,ServiceNow'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     Search Algorithm  Sorting Algorithm     Asked in 2 Companies      basic        frequent

 Q8. Write an algorithm / Java Program to show duplicates in an array of n elements?Algorithm
Ans. int duplicateArray[] = { 1, 2, 2, 3, 4, 5, 6, 8, 9}
Set unique = new HashSet();
for (int i = 0; i < duplicateArray.length; i) {
if (unique.contains(duplicateArray[i])) {
System.out.println(duplicateArray[i]);
} else {
unique.add(duplicateArray[i]);
}
}

Complexity O(n) = nHashSet contains and add has O(n) = 1

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 Q9. What is a binary tree ?Algorithm
Ans. Binary tree is a tree in which each node has up to two children.Tree is a data structure composed of nodes.Each tree has a root node(not necessary in graph theory). The root node has zero or more child nodes.Each child node has zero or more child nodes, and so on.The tree cannot contain cycles.

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   Like         Discuss         Correct / Improve     binary tree     Asked in 1 Companies

 Q10. 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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   Like         Discuss         Correct / Improve     LinkedList  Data structures  Algorithm

 Q11. Which sorting algorithm is used by Collections.sort() in Java ?Core Java
Ans. The sorting algorithm is a modified mergesort. This algorithm offers guaranteed n log(n) performance.

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 Q12. 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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 Q13. Find the repeating number using O(n) time and constant space.Algorithm
Ans. http://www.geeksforgeeks.org/find-duplicates-in-on-time-and-constant-extra-space/

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 Q14. Explain Travelling SalesMan Problem ?Algorithm
Ans. https://en.wikipedia.org/wiki/Travelling_salesman_problem

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 Q15. Write an Algorithm for Graph Traversal ? The Graph has a loop.Algorithm
Ans. Please not that all such questions can be easily answered through recursion.

Simple recursive implementation could be

traverse(root);

void traverse(Element element){
if(element.hasNext()){
traverse(element.next());
} else {
System.out.println(element);
}
}

but this algo / code lead to endless loop if there is a loop in graph traversal.

So you can keep a collection to keep track of which elements have laready been traversed


static List<Elements> listOfAlreadyTraversedElements = new ArrayList<Elements>();

main(){
traverse(root);
}

void traverse(Element element){
if(element.hasNext()){
traverse(element.next());
} else {
listOfAlreadyTraversedElements.add(element);
System.out.println(element);
}
}

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 Q16. Flatten a Binary Tree to Linked ListAlgorithm
Ans. https://www.geeksforgeeks.org/flatten-a-binary-tree-into-linked-list/

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 Q17. Write an algorithm / java program for Heap Sort ?Algorithm
Ans. https://www.geeksforgeeks.org/heap-sort/

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 Q18. Write any sorting algorithm.Algorithm
Ans. https://javasearch.buggybread.com/InterviewQuestions/questionSearch.php?searchOption=label'

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   Like         Discuss         Correct / Improve     Algorithm  Sorting Algorithm     Asked in 4 Companies      basic        frequent

 Q19. How to create list that will sort it's elements dynamically?Algorithm
Ans. Override the behavior of collection class to sort the list upon each element addition. Though it's not recommended as list are sorting heavy data structures.

List<MyType> list = new ArrayList<MyType>() {
public boolean add(MyType mt) {
super.add(mt);
Collections.sort(list, comparator);
return true;
}
};

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   Like         Discuss         Correct / Improve          Asked in 1 Companies      intermediate

 Q20. Write program to create a linked list and perform different operations on it.Algorithm
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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 Q21. Explain bubble sort.Algorithm
Ans. array is traversed from first element to last element. Here current element is compared with next element. If current element is greater than next element it is swapped.

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 Q22. Write code to check if a Binary tree is symmetricalAlgorithm
 This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.


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   Like         Discuss         Correct / Improve     binary tree     Asked in 1 Companies

 Q23. Write a function that returns the depth of a tree.Algorithm
 This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.


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 Q24. Write code to find the node where two linked lists intersect.Algorithm
 This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.


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 Q25. Check if tic tac toe has a winnerAlgorithm
 This question was recently asked at 'Microsoft'.This question is still unanswered. Can you please provide an answer.


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 Q26. Write program to balance a binary treeAlgorithm
 This question is still unanswered. Can you please provide an answer.


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 Q27. Given a graph, find if it represents a treeAlgorithm
Ans. We can simply find it by checking the criteria of a tree. A tree will not contain a cycle, so if there is any cycle in the graph, it is not a tree. We can check it using another approach, if the graph is connected and it has V-1 edges, it could be a tree. Here V is the number of vertices in the graph

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 Q28. Explain different sorting algorithms and Big O of eachAlgorithm
 This question was recently asked at 'Microsoft,ServiceNow'.This question is still unanswered. Can you please provide an answer.


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 Q29. Write a program to find loop in a linked listAlgorithm
 This question was recently asked at 'Microsoft'.This question is still unanswered. Can you please provide an answer.


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 Q30. How to convert a bst to doubly linked listAlgorithm
 This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.


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