Client Server Architecture

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Pine Labs Interview Experience

Process: 3 Technical Round + 1 Manager Round + 1 HR


Round 1:

• Write Code to find meeting point in Y Linked List ( 7 in below list)

• Write your own Copy constructor, assignment operator for below class

           class Student
           {
                  char* name;
                  int age;
                  vector<Subject*> optionSubject;
           }
           where Subject is defined as below
           struct Subject
           {
                 char* name;
                 int marks;
           }

Round 2:

•  Write Code to find LCA of Binary Search Tree of given node & if node is not there return NULL.
• Design Logger class considering multithreading aspect (ensuring Race condition is avoided)
• Design Memory Manager ( Define Data structure of it and handle memory allocation & deallocation )

Round 3:

• Asked me Round 1 question of Y List again. After I told him that its already asked he modified the question by introducing a loop in starting & then find the meeting pointed i.e 7

•  Questions related to C++
• What is static keyword , why we need static data member & member functions.
• What is static const ? Where do you define in class & initialize it.
• Can Destructor throw an exception?
• Can Constructor throw an exception? Can we use the data member already initialized before throwing exception?

Round 4 (CTO Round):

• Asked me to introduced myself & explain projects i have worked upon. Then he asked few questions related to project.
• Write Code of thread Safe Singleton class.
• General Discussion.

Round 5 (HR Round):

• Explained about the company, its growth story different policies & work environment.
• General Questions.
• Current CTC & Expectation.

Overall, You need to be good in Data Structures & Design to crack Pine Labs Interview.

Ciena Interview Experience

Coming Soon

Comma Operator inside for loop Condition in C++

You may have used Comma operator in initilialization and increment part of for loop like below

                 for(init;condition;increment) --> for(int i=0,j=5;i<j;i++,j--)

But can we used Comma operator inside for loop condition ?

The answer is Yes but it behave bit differently.

Predict the output of below program

void commaOperator()
{
    int i=0,j=0;
    cout<<"Using && inside for loop Condition"<<endl;
    for(;i<4&&j<6;)
    {
            cout<<i<<" "<<j<<endl;
            i++;
            j++;
    }
    cout<<"Using comma inside for loop Condition "<<endl;
    i=0,j=0;
    for(;i<4,j<6;)
    {
            cout<<i<<" "<<j<<endl;
            i++;
            j++;
    }

}

Output:

Using && inside for loop Condition
0 0
1 1
2 2
3 3
Using comma inside for loop Condition
0 0
1 1
2 2
3 3
4 4
5 5

As Comma operator is a binary operator it evaluates first operand but discards its result and then evaluates the second operand and returns its result.
In above example , for loop will run till second condition is true (j<6 ) and discards the first condition.

But what if we use comma operator in assignment like below
int a=5,b=7,c;
c=a,b;

Here c will be equal to a (5) as assignment has higher precedence than comma operator.


Please comment if you find anything incorrect.

Find Consecutive Elements in Unsorted Array in O(n) - C++ Code

#include<iostream>
#include<set>

int findConsecutiveElements(int arr[], int n)
{
        std::set<int> s;
        int ans = 0;

        for (int i = 0; i < n; i++)
                s.insert(arr[i]);

        for (int i=0; i<n; i++)
        {
                if (s.find(arr[i]-1) == s.end())
                {
                        int j = arr[i];
                        while (s.find(j) != s.end())
                                j++;

                        ans = std::max(ans, j - arr[i]);
                }
        }
        return ans;
}

int main()
{
        int arr[] = {1,21, 24, 25, 9, 3, 11, 4, 20, 22,23};
        int n = sizeof arr/ sizeof arr[0];
        std::cout << "Length of the Longest consecutive elements is "
                << findConsecutiveElements(arr, n);
        return 0;
}

Kth smallest element in a BST - C++ Code

Do inorder Traversal of BST and count number of elements traversed till now . As inorder traversal gives us the element in sorted Order, when count reaches k , we break out and Print the element.

/**
 * Definition for Binary Search Tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 * };
 */
int kthsmallest(TreeNode* root, int k) {
    if(root==NULL)
      return 0;
    stack<TreeNode*> s;
    bool complete=false;
    TreeNode* cur=root;
    int count=0;
    int val=0;
    while(!complete)
    {
        if(cur!=NULL)
        {
            s.push(cur);
            cur=cur->left;
        }
        else
        {
            if(!s.empty())
            {
                count++;
                cur=s.top();
                s.pop();
                if(count==k)
                {
                    val=cur->val;       
      break;
                }
                  cur=cur->right;
            }
            else
              complete=true;
        }  
    }
    return val;
}

Please comment if you find anything incorrect.

First Non Repeating Character in String

#include<iostream>
#include<string>
#include<memory>
#include<climits>
#define NUMBER_OF_CHARS 256
using namespace std;
struct CountIndex
{

 int count;
 int index;
};
char getFirstNonRepeatngCharacter(const string& str)
{
 char ch=' ';
 unique_ptr<CountIndex[]> ci(new CountIndex[256]());
 //Can also use shared_ptr
 //shared_ptr<CountIndex> ci(new CountIndex[256](),std::default_delete<CountIndex[]>());
 for(auto& it:str)
 {
  ci.get()[it].count++;
  if(ci.get()[it].count==1)
   ci.get()[it].index= &it - &str[0];
  else

   ci.get()[it].index= ci.get()[it].index;

 }
 int maxIndex=INT_MAX;

 for(int it=0;it<NUMBER_OF_CHARS;it++)
 {
  if(ci.get()[it].count==1 && ci.get()[it].index <maxIndex)
  {
   maxIndex= ci.get()[it].index;

  }
 }
 return maxIndex!=INT_MAX?str[maxIndex]:' ';
}
int main()
{    
 string str ;
 cin>>str;
 char ch=getFirstNonRepeatngCharacter(str);
 if(ch !=' ')
  cout<<" First Non repeating Character is "<< ch;
 else
  cout<<" No Repeating Character Exist ";


}

Folder Organizer

import os,errno
import sys,getopt
def main(argv):
    inputDir=''
    try:
        opts,args= getopt.getopt(argv,"hi:",["iDir="])
    except getopt.GetoptError:
        print 'DirectoryOrganizer.py -i <inputDirectory>'
        sys.exit(2)
    for opt,arg in opts:
        if opt == '-h':
            print 'DirectoryOrganizer.py -i <inputDirectory>'
            sys.exit()
        elif opt in ("-i","--iDir"):
            inputDir=arg
    files= os.listdir(inputDir)
    for file in files:
        extension= os.path.splitext(file)[1][1:]
        if extension:
            fileInputDir =inputDir+extension
            try:
                if not os.path.isdir(fileInputDir):
                    os.makedirs(fileInputDir)
                if not os.path.isfile(fileInputDir+"\\"+file):
                    os.rename(inputDir+file,fileInputDir+"\\"+file)
                else:
                    print "file with same name already exist in folder "+ fileInputDir+"\\"+file
            except OSError as e:
                if e.errno != errno.EEXIST:
                    raise

if __name__ == "__main__":
main(sys.argv[1:])

Allocating Void pointer memory using new operator

I was Implementing Generic List in C++ and was able to successfully allocate memory of void*  data using malloc ( malloc return void *) . But how about using new. Can we do below

void Test()
{
           void *f= new void[25];  //void *f=malloc(25); --> Works
           delete f;
}

The Answer is NO.
Because void has no size . How much space has to be allocated is not known.

So if you need to allocate memory using new use operator like

void Test()
{
          void *f=operator new(25);
          delete f;
}

Floyd Washall Algorithm Code in Java

We are given a directed graph and if we need to find out minimum distance between all the sources and destinations, we will use Floyd Warshall All Pair Shortest Path Algorithm.
Suppose we are given below graph

import java.util.*;
import java.lang.*;

public class Floyd
{
 final static int INF=Integer.MAX_VALUE;
 void Path(int graph[][],int n)
 {
   int minDistance[][]=new int[n][n];
   for(int i=0;i<n;i++)
   {
    for(int j=0;j<n;j++)
    {
     minDistance[i][j]=graph[i][j];
     
      
    }
   }
   for(int k=0;k<n;k++)
   {
    minDistance[k][k]=0;
   }
   
   for(int k=0;k<n;k++)
   {
    for(int i=0;i<n;i++)
    {
     for(int j=0;j<n;j++)
     {
          if(minDistance[i][j]>minDistance[i][k]+minDistance[k][j] && minDistance[i][k] !=INF && minDistance[k][j]!=INF)   
          minDistance[i][j]=minDistance[i][k]+minDistance[k][j];
     }
    }
   }
  
  printMatrix(minDistance,n);
  
 }
  void printMatrix(int minDistance[][],int n)
  {
   for(int i=0;i<n;i++)
   {
    for(int j=0;j<n;j++)
    {
         System.out.print(minDistance[i][j]+ "  ");
    }
    System.out.println();
   }
   
  }
 public static void main(String[] args)
 {
  int a[][]={{0,5,INF,10},
             {INF,0,3,INF},
             {INF,INF,0,1},
             {INF,INF,INF,0}};
  Floyd f=new Floyd();
  f.Path(a,4);
 }
}

Puzzle - Given 10 points in Space, create a Closed Figure with 4 points in each Line

I recently stumbled upon a problem in which we need to create a  Closed Figure from 10 points in Space with constraint that we must include 4 points in any Line we use to create the figure.
Think about the solution before Reading the solution

Solution :
Create a Star Like below which satisfies the requirement with Yellow dots representing points used

                         


Please comment if you have any other solution for this  

Static Assertion in C++11

Pre C++11 , we had  run time assertion function assert(). If assertion fails , a message will be written to console  and abort() will be called, terminating the program execution at run time. As assert() works only when control passes over the assertion, there is a possibility that a failing run-time assertion may lay dormant, undetected for long period of time.

#include<iostream>
#include<cassert>
class A
{
    int x;
    public:
       A(int a):x(a){}
       int getX(){ return x; }
};
int main()
{
   A a(17);
   assert(a.getX()<10);
   std::cout<< "Assertion a.getX()<10 pass";
   return 0;
}

Above program will compile fine, even though assert condition is false but we got the failure only at runtime.

Output:

assertion "a.getX()<10" failed: file "assert.cpp", line 16, function: int main()

Aborted (core dumped)

Therefore C++11 introduced Compile time Assertion functionality using static_assert(). As Compilation will fail, developer will be aware of the problematic portion of the code and track bugs early in development phase. Also For Example, if some functionality of code critically depends on size of int to be exactly 4 bytes, we can use static_assert like below

#include<iostream>
class A
{
    public:
    static const int b = 3;
};
int main()
{
    static_assert(A::b > 4, "A::bar is less than 4");
    static_assert(sizeof(int) == 4,"size of integer is not 4 bytes");
}

static_assert can be also used to check whether class is default constructable or can be constructed with certain parameters or  can be copied or is movable or assignable using trivial/non trivial constructors.

#include<iostream>
class A
{
    int x;
    public:
       A():x(0)        
       {

       }
       A(int a):x(a)
       {

       }
};
int main()
{
    static_assert(std::is_constructible<A>::value, "Class is not constructible");
    static_assert(std::is_trivially_constructible<A>::value," Class is not trivially constructible ");
    static_assert(std::is_constructible<A,char,int>::value, "Class is not constructible with char,int ");
 static_assert(std::is_trivially_copy_constructible<A>::value,"Class is not trivially copy constructible");  
    return 0;
}

Output:

static_assert_constructors.cpp: In function ‘int main()’:

static_assert_constructors.cpp:20:9: error: static assertion failed:  Class is not trivially construtible

         static_assert(std::is_trivially_constructible<A>::value," Class is not trivially construtible ");

         ^

static_assert_constructors.cpp:21:5: error: static assertion failed: Class is not constructible with char,int

     static_assert(std::is_constructible<A,char,int>::value, "Class is not constructible with char,int ");

Few Other standard values introduced in C++11, that  you can use with static_assert are:

• std::is_move_assignable<T>::value,
• std::is_nothrow_copy_constructible<T>::value
• std::is_trivially_copyable<T>::value
• std::is_copy_assignable<T>::value
• std::is_default_constructible<T>::value
• std::is_assignable<T>::value