C++ interview Questions for Experinced persons

1. overload new operater.

2. Difference between Op new and new operator

3. Explain placement new and why n when it is used

4. is there a placement delete.

5. Explain the error when new fails

6. malloc vs new

7.what is name mangling

8.what are proxy objects ?

9.what is a local class ,sub class ,nested clasd

10.what is object slicing.

11. What is name hiding

12. Explain vtable in detail
       http://www.go4expert.com/articles/virtual-table-vptr-t16544/
       http://www.learncpp.com/cpp-tutorial/125-the-virtual-table/

13.what is a conversion constructor

14.explain explicit constructor

15.copy constructor vs overloaded assignment operator

16.what are class invariants

17.implement a final class in cpp

18.Write a singleton pattern.is it threadsafe ?where it is used.

19.how stl map is implemented internally??

20.how vector allocate memory or how it works internally.can you write your own vector ?

21.what are smart pointers .unique_ptr vs auto_ptr vs shared_ptr?

22. Queue vs priority queue.can you implement or write your own priority queue.

23. Vector vs list vs deque vs map. Which one should u use under what situation

24.what are function pointers , call back functions. What are advantages

25.list x ;list x(); what is the difference here

26.what is synchronous and asynchronous calls/functions or operations

27.what tools u have used for performace checking.how u detect memory leaks.

   Explain how you can detect memory leak,memory corruption.what is dangling pointer

28.have u worked with gdb ,dbx,valgrind ??

29.overloading on const

30.design patterns used in ur project. Explain and write abstract factory,visitor etc

31.how to remove duplicates from vector with single traversal.

32.why private constructor is used. how to handle exceptions in a constructor ?and do we need to handle exceptions in destructor ??

https://isocpp.org/wiki/faq/exceptions#selfcleaning-members

33.How iterator invalidation works in vector,dq,list

34.efficient method of removing odd elements from vector

33.how to sort a vector containing pair elements

34.how to add an element to the front of a vector

35.difference between map::find() vs map::operator[ ]

36.are pure virtual methods allowed in a template class

37.can we have static virtual function

38. Function pointer vs function objects

39.map vs hash_map

40.why should you use obj.empty() over (obj.size() ==0) to check emptiness

41.difference between conversion function and overloaded function call operator

42. Implement pre and post increment operator.

43.how reserve() , capacity() and resize() works in vector

44.what is infamous swap trick on vector ? How to downsize a vector

45.should we use global find algorithm or member function find() for map/set ?

46.how to call/use base class virtual function by a derived class which has already ovrridden it ?

47.can virtual function be private ??

48.issues with pass by value of a class object

49. Int *p=null ; int &p=null ; are they  wrong/correct ??

50.pimpl idiom

51.How to initialize const member variables of a class ??
52. this vs *this
      http://stackoverflow.com/questions/2750316/this-vs-this-in-c
53.calculate the Size of object of a class
54.Write a non-inheritable class(final class)
      http://www.geeksforgeeks.org/simulating-final-class-in-c/
      http://stackoverflow.com/questions/1366441/final-class-in-c

55.Smart pointers , boost::shared_ptr or std::unique_ptr
  

std::shared_ptr<int> p1(new int(5));
std::shared_ptr<int> p2 = p1; //Both now own the memory.

p1.reset(); //Memory still exists, due to p2.
p2.reset(); //Deletes the memory, since no one else owns the memory.

56. New features in c++14
   auto and lambda,std::move constructor ,forward
57.Why do I need to return *this in an assignment operator function?
   To make assignment such as (obj3 = obj2) = obj1; to work.
58.Cache locality,SFINAE 
59.What is the difference between std::vector<int> x; and std::vector<int> x() ?
  First one declares a variable x of type std::vector. Second one declares a function x which returns       std::vector.
60. How to initialize constant and reference member variable?
  Using initialization list.
61.How would you delete object of singleton class?
  we can follow is “Reference counting” mechanism
62. factory vs Abstract factory
    http://www.codeproject.com/Articles/492900/From-No-Factory-to-Factory-Method
   http://corey.quickshiftconsulting.com/blog/first-post
63.How thread synchronization done for pthreads
     http://www.bogotobogo.com/cplusplus/multithreading_pthread.php
64.How to debug threads in dbx/gdb
65.How to use c code in c++
65.What will the sizes of base and derived class object.
http://www.go4expert.com/articles/size-cpp-class-object-t16676/

class Base
{       char ch;
         int value;
        static double db;
    public:
        Base(){}
        virtual ~Base(){}      
        virtual void func() {}
};

class Derived : virtual public Base
{     int d1;
    public:
       void func(){}      
       virtual void func2(){}
};

Ans: Base b is of size=1byte char+3byte padding+4byte int+1 byte vtable pointer=12bytes
        Derived d=(12 bytes of Base)+ 4 byte Int + 4 Byte for Virtual derivation =20 bytes

66. Write your own C++ like exceptional Handling in c.(oracle second round)

http://www.on-time.com/ddj0011.htm
http://stackoverflow.com/questions/4448677/can-a-c-program-handle-c-exceptions

67.Write a c program to dump data from a table having 20K records.;without using Pro*C.
  OCI ??
    https://github.com/vrogier/ocilib
    https://vrogier.github.io/ocilib/doc/html/group___ocilib_c_api_statements.html
68.How to create rest APIs in c.
69.Implement Stack using two queues.
  http://stackoverflow.com/questions/688276/implement-stack-using-two-queues
  http://www.geeksforgeeks.org/implement-stack-using-queue/

Simple wordpress AJAX submit example

Follow these simple steps.

1. Create a button on the page i.e. maybe on index page

       <input class="ajax-link" type="button" value="AJAXSUBMIT">

2. we will pass the text data "client side data" and get the response from server as "received data:" "client side"


3. create a file myajax.js under themes 'js' folder having below content

    jQuery(document).ready( function($) {
$(".ajax-link").click( function() {
var data = {
action: 'test_response',
                        post_var: 'client side '
};
// the_ajax_script.ajaxurl is a variable that will contain the url to the ajax processing file
$.post(the_ajax_script.ajaxurl, data, function(response) {
alert(response);
});
return false;
});
});

4. open the functions.php file from themes folder
5. Add the javascript and localize the ajaxurl

function test_ajax_load_scripts() {
// load our jquery file that sends the $.post request
wp_enqueue_script( "ajax-test",get_template_directory_uri() . '/js/myajax.js', array( 'jquery' ) );

// make the ajaxurl var available to the above script
wp_localize_script( 'ajax-test', 'the_ajax_script', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) );
}
add_action('wp_print_scripts', 'test_ajax_load_scripts');

 

6. Add the below in functions.php to process ajax data from cleint side

function text_ajax_process_request() {
// first check if data is being sent and that it is the data we want
  if ( isset( $_POST["post_var"] ) ) {
// now set our response var equal to that of the POST var (this will need to be sanitized based on what you're doing with with it)
$response = $_POST["post_var"];
        $server_text= "received data: ";
// send the response back to the front end
echo $server_text.$response;
die();
}
}
add_action('wp_ajax_test_response', 'text_ajax_process_request');
add_action('wp_ajax_nopriv_test_response', 'text_ajax_process_request');

Here is the result