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Algorithm - Interview Questions and Answers for 'Algorithm' - 63 question(s) found - Order By Newest

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Advanced level question frequently asked in US based companies. Recently asked in EMC and Intuit.

Q1. Can you provide some implementation of a Dictionary having large number of words ?

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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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_{Like Discuss Correct / Improve java collections hashmap binary search search algorithm advanced architecture data structure Asked in 6 Companies frequent}

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Q2. What is the difference between Graph's Breadth first and Depth First algorithm ?

^{2017-07-23 10:12:58}

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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Q3. In a Linked list with sorted numbers, insert a new numbers while maintaining the sort order.

^{2017-07-25 14:59:01}

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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Q4. What are the pre-requisite for the collection to perform Binary Search ?

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Ans. 1. Collection should have an index for random access.
2. Collection should have ordered elements.

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Q5. Write an algorithm / Java Program to show duplicates in an array of n elements?

^{2017-01-19 15:37:26}

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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Q6. What is a binary tree ?

^{2017-01-19 15:38:04}

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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Q7. Write a program for LinkedList, with method to append node and traversing the list ?

^{2017-07-25 14:31:33}

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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Q8. Write a Program for Graph Depth First Traversal using Apache Commons MultiMap

^{2017-07-23 10:01:14}

Ans. import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;

public class Graph {
   private static Multimap<Integer,Integer> adjacentDirectedNodesMap = ArrayListMultimap.create();
   private static Set<Integer> alreadyVisited = new HashSet();

   static{
      adjacentDirectedNodesMap.put(1, 2);
      adjacentDirectedNodesMap.put(1, 3);
      adjacentDirectedNodesMap.put(1, 5);
      adjacentDirectedNodesMap.put(2, 4);
      adjacentDirectedNodesMap.put(4, 5);
   }

   public static void main(String[] args){
      ArrayList visited = new ArrayList();

      Integer startNode = 1;

      displayAdjacentNodes(startNode);

   }

   private static void displayAdjacentNodes(Integer integer){
      if(alreadyVisited.contains(integer)){
         return;
      }
      alreadyVisited.add(integer);
      System.out.println(integer);
      for(Integer adjacentNodes: adjacentDirectedNodesMap.get(integer)){
         displayAdjacentNodes(adjacentNodes);
      }
   }

}

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Q9. Which sorting algorithm is used by Collections.sort() in Java ?

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Ans. The sorting algorithm is a modified mergesort. This algorithm offers guaranteed n log(n) performance.

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Q10. How to determine if the linked list has a cycle in it ?

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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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Q11. Find the repeating number using O(n) time and constant space.

Ans. http://www.geeksforgeeks.org/find-duplicates-in-on-time-and-constant-extra-space/

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Q12. Explain Travelling SalesMan Problem ?

^{2016-11-21 15:21:21}

Ans. https://en.wikipedia.org/wiki/Travelling_salesman_problem

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Q13. Write an Algorithm for Graph Traversal ? The Graph has a loop.

^{2016-11-30 15:42:32}

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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Q14. Flatten a Binary Tree to Linked List

^{2016-12-13 14:49:54}

Ans. https://www.geeksforgeeks.org/flatten-a-binary-tree-into-linked-list/

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Q15. Explain various Searching and Sorting Algorithms ?

^{2017-01-11 16:05:54}

Ans. a

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Q16. Write an algorithm / java program for Heap Sort ?

^{2017-01-19 15:36:18}

Ans. https://www.geeksforgeeks.org/heap-sort/

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Q17. Write any sorting algorithm.

^{2017-01-25 13:41:50}

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}

Q18. How to create list that will sort it's elements dynamically?

^{2017-02-21 12:47:22}

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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Q19. Write program to create a linked list and perform different operations on it.

^{2017-02-24 14:18:01}

^{This question was recently asked at 'Kony Labs,Compro Technologies'.This question is still unanswered. Can you please provide an answer.}

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Q20. Explain bubble sort.

^{2017-03-03 14:28:51}

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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Q21. Write code to check if a Binary tree is symmetrical

^{2017-03-03 14:29:12}

^{This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.}

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Q22. Write a function that returns the depth of a tree.

^{2017-03-03 14:38:46}

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Q23. Write code to find the node where two linked lists intersect.

^{2017-03-03 14:39:39}

^{This question was recently asked at 'Amazon'.This question is still unanswered. Can you please provide an answer.}

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Q24. Check if tic tac toe has a winner

^{2017-03-03 14:40:05}

^{This question was recently asked at 'Microsoft'.This question is still unanswered. Can you please provide an answer.}

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Q25. Write program to balance a binary tree

^{2017-03-03 14:40:54}

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Q26. Given a graph, find if it represents a tree

^{2017-03-03 14:41:06}

^{This question was recently asked at 'Google'.This question is still unanswered. Can you please provide an answer.}

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Q27. Explain different sorting algorithms and Big O of each

^{2017-03-03 14:41:45}

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Q28. Write a program to find loop in a linked list

^{2017-03-03 14:42:17}

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Q29. How to convert a bst to doubly linked list

^{2017-03-03 14:42:30}

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Q30. How do we implement a weight round robin algorithm in load balancing ?

^{2017-03-19 19:31:41}

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Q31. Given the list of adjacent nodes, What will be the Breadth First path

1 -> 2
1 -> 3
1 -> 6
2 -> 4
3 -> 5

^{2017-07-23 10:30:20}

Ans. 1 -> 2 -> 3 -> 6 -> 4 - > 5

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Q32. Given the list of adjacent nodes, What will be the Depth First path

1 -> 2
1 -> 3
1 -> 6
2 -> 4
3 -> 5

^{2017-07-23 10:30:48}

Ans. 1 -> 2 -> 4 -> 3 -> 5 -> 6

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Q33. What will happen in a graph traversal if we don't have a check for cycle

^{2017-07-23 10:32:30}

Ans. It will result in never ending loop

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Q34. Describe how you could use a single array to implement three stacks

^{2018-05-24 08:28:08}

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Q35. How would you design a stack which, in addition to push and pop, also has a function min which returns the minimum element? Push, pop and min should all operate in O(1) time

^{2018-05-24 08:30:09}

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Q36. 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

^{2018-05-24 08:33:37}

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Q37. How different is the Search algorithm when we query Cassandra Tables and When we query Oracle Tables ?

^{2017-08-18 09:40:40}

Ans. Relational Database uses linear search if we don't query using indices. Performance for linear search is O(n). If indices have been used , relational database uses binary search. Performance for binary search is O(Log n).

Casandra uses hash search. Performance for Hash Search is O(1).

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Q38. Find Max from Stack in O(1) complexity

^{2018-01-21 17:13:23}

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Q39. Explain Binary Search

^{2018-02-02 08:37:31}

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Q40. Find all paths of length L in an acyclic graph

^{2018-02-10 12:04:08}

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