The basic idea of selection sorting algorithm is

1)find minimum element in the list
2)swap it with the beginning element
3)repeat the above steps after moving pointer to next element

Here is the graphical representation of operation of this algorithm…

Before we go to linked list sorting understand how do we sort for an array…
Here is the C code for selection sort for an array

void selectionsort(int a[], int size)
{
  int i, j, min, tmp;
 
  for (i = 0; i < size - 1; i++)
  {
    min = i;
    for (j = i+1; j < size; j++)
      if (a[j] < a[min])
        min = j;
 
    //swap(a[i], a[min]);
    tmp = a[i];
    a[i] = a[min];
    a[min]=tmp;
  }
}

While sorting linked list, deal with these points carefully..
1)min node and node to be swapped are far apart, swapping routine should need to take care of this
2)min node and node to be swapped are neighbors, so just swap them
3)node to be swapped is header node, then list header node has to be changed (i.e. min node need to be assigned)

take a look at the pointers swapping while swapping neighboring nodes(on of the node to be swapped is header node)

and here is several passes of this algorithm (result of sorting linked list)…

Here is the program (for sorting linked list using selection sort)..

Node *selectionsort(Node *list)
{
  Node *tmp=list, *tmp2, *prev, *iLst, *jLst;
  Node *min;
 
  if (!list)
  {
    //empty list no need sort
    return list;
  }
 
  //swapping the nodes we require previous node (remember this is SLL)
  prev = list;
 
  for (iLst=list; iLst && iLst->next; iLst=iLst->next) 
  {
    min = iLst;
    for (jLst = iLst->next; jLst; jLst = jLst->next)
    {
      //get the minimum node
      if (jLst->info < min->info) 
      {  
        //mark the minimum node we had encountered so far
        min = jLst;
      } 
    } 
    //swap the nodes if required 
    if (iLst != min)
    {
      tmp = min->next;
 
      //go find min's previous node (min node can be many nodes away from base node to be swapped)
      for (tmp2=iLst;tmp2->next; tmp2=tmp2->next)
      {
        if (tmp2->next == min)
        {
          break;
        }
      }
 
 
      //check whether node to swapped is in beggining (i.e. header node)
      if (prev != iLst)
      {
        prev->next = min;
      }
      else
      {
        //as we do not have special header node, if the first node and some 
        //other node, need to be swapped, then update the list (makes new min node as 
        //logical header)
        list = min;
      }
 
      //are nodes to be swapped neibgoring nodes?
      if (iLst->next == min)
      {
        //nodes to be swapped are neibhoring nodes,
        //then swap them simply
        min->next = iLst;
        iLst->next = tmp;
      }
      else
      {
        //nodes to be swapped are not neibhor nodes, they are apart
        //so, consider all scenarios
        min->next = iLst->next;
 
        iLst->next = tmp;
        tmp2->next = iLst;
      }
 
      //after swapping we've changed our iterator address, so 
      //assign correct position to contnue sorting..
      iLst = min;
    }
 
    //readjust previous node before we move our list pointer
    prev = iLst;
  }
  return list;
}

downlaod full [source code]

Popularity: 45%

Please refer this post for linked list basics and all other operations on linked lists.

 

Loops in linked list can be detected by inserting dummy nodes after every node, so if we find dummy node after a node already, that says that list has a loop. The diagram below explains this. This method takes O(n) time and O(n) additional space.

Loops in linked list can also be detected by running two loops paralally, one loop traverse list by one node, another loop traverse list by skipping a node while going to next node. this way they meet at some point of time, if the list has a loop. The diagram below explains this. This method takes O(n) time in best case.

program for finding loop by traversing with two pointers… this program takes input as linked list, returns a node(where a loop starts), or returns NULL if we could not find a loop…

Node *detectloop(Node *list)
{
  Node *n1, *n2;
 
  //prev indicates loop started at this point
  Node *prev=NULL; 
 
  for(n1=list, n2=list; (n1!=NULL) && (n2!=NULL); )
  {
    if (prev && (n1 == n2))
    {
      return prev;
    }
    prev = n1;
    n1=n1->next;
    n2=n2->next;
    if (n2)
    {
      n2=n2->next;
    }
  }
}

comments?

Popularity: 22%

I have written a program for printing array in spiral order (iterative version) in an earlier post. Here, in this post let us see how we can make this algorithm even simpler using recursive routine.

the logic behind this routine is explained in the below diagram.

in C, array is stored in row major order, we can get address of any element (arr[row][column]) using

arr + (row * sizeof(elementType)*MAX_COLS) + column

so we are taking advantage of this layout (row major order), and printing rings by rings by updating the base address and num of columns, and num of rows.

here is the routine…

#define MAX_COLS 20
 
int print_array_spirally(int arr[][MAX_COLS], int num_rows, int num_cols)
{
  int i;
 
  if ((num_rows<=0) || (num_cols<=0))
  {
    return 0;
  }
 
  if (num_rows < 2 || num_cols < 2)
  {
    //deal with 1xN, Nx1 arrays
    for(i=0; (num_cols-1) && (i<num_cols); i++)
    {
      printf("%d ", arr[0][i]);
    }
 
    for(i=0; (num_rows-1) && (i<num_rows); i++)
    {
      printf("%d ", arr[i][0]);
    }
    return 0;
  }
 
  for(i=0; i<num_cols; i++)
  {
    printf("%d ", arr[0][i]);
  }
 
  for(i=0; i<num_rows-1; i++)
  {
    //exclude top column number as it is printed part of row
    printf("%d ", arr[i+1][num_cols-1]);
  }
 
  for(i=1; i<=num_cols-1; i++)
  {
    //exclude bottom right number as it is printed part of column
    printf("%d ", arr[num_rows-1][num_cols-i-1]);
  }
 
  for(i=1; i<=num_rows-2; i++)
  {
    //exclude bottom left and top, left numbers as they are already printed
    printf("%d ", arr[num_rows-i-1][0]);
  }
 
  //array stored in row-major order
  print_array_spirally((char *)arr+(sizeof(int)*(1+MAX_COLS)), 
                       num_rows-2, 
                       num_cols-2);
 
  return 0;
}
 
#ifdef TEST
int main()
{
  int arr[][MAX_COLS] = {{1, 2, 3, 10, 17}, {4, 5, 6, 11, 18}, {7, 8, 9, 12, 19}, {13, 14, 15, 16, 20}};
 
  print_array_spirally(arr, 4, 5);
}
#endif

download full [source code]

comments are always welcome…

Popularity: 14%

There is no difference but UNIX is a multitasking, multi-user OS unlike DOS. In DOS, serial multi-tasking can be achieved but it makes the computer work less efficiently. If, for example, there was some calculation being done and we called in Sidekick, then all work on the calculations would stop as the computer responded to Sidekick. Wouldn’t it then be far better to give Sidekick only a part of the computer’s time? So that even while we were in Sidekick the calculations would carry on being performed in the background.

Under UNIX, all we have to do is to compile and link the background while we carry on doing whatever else we want in the foreground.

Background Process:

main()
{
  long l;
  for(i=0;i<=4000000;i++);
    printf("l is %d \n",i);
}

1)Compile it at UNIX prompt by saying CC<program name>.

2)The file generated will be a.out.

3)Execute it through the command a.out &. The & will make it a background process which is terminated only if process ends, or is interrupted with a DEL.

The UNIX prompt will come back on screen immediately. Load the editor again and wait. After some time a l is 4000000 will be displayed at the top left corner of the screen.

Isn’t this more convenient than DOS’s single tasking environment?

UNIX is able to switch between processes because each process has an identification number. This identification number identifies the variables and REGISTER values that are associated with this process. These variables are in a state of limbo when the process is suspended. And get activated again once the microprocessor resumes execution of the process. 

Process Identification:

/*There is a UNIX function getpid()- that enables us to get the identification number of a process*/

main()
{
  int pid;
  pid=getpid();
  print("Process ID is %d\n",pid);
}

The pid value will depend on the number of processes already running. It will always be unique.

Parent And Child:

A process in UNIX is not a stand-alone. This results in a parent-child relationship existing between processes.

main()
{
  int ppid;
  ppid=getppid();
  print("Parent Process ID is %d\n",ppid);
}

This program will give the ID number of its parent. So who is this parent?

When we boot the system, a special process called the SWAPPER or SCHEDULER is created with a PID of 0. The SWAPPER manages memory allocation for processes and influences CPU allocation. The SWAPPER in turn creates three children:the process dispatcher, vhand and bdflush with ID numbers 1,2,3 respectively.

This is done by executing the file init which exists in the etc sub-directory. The dispatcher now gives birth to the shell. From now on all processes initiated by us are children of the shell.

The fork():

Processes initiated by us can also create children in the same manner as the swapper and the process dispatcher did. These children processes are created using the fork() function. It is by forking processes that we can exploit the multitasking capability of UNIX.

main()
{
  fork();
  printf("Hello World\n");
}

Can you guess what the output of this program will be?

The statement Hello World will be displayed twice on screen. The fork() creates a child that is a duplicate of the parent process. The parent process in this case being the program listed above. Since now there are two identical processes in memory, the Hello World is printed twice.

The moment a call is made to the fork(), a child process is created. The child copy, too, gets a copy of the variable pid, but with a value of 0 by default. The parent process, is returned a value greater than 0 by the fork().

For UNIX is more than just a multi-tasking OS. It also has the facility to enable many users to access the machine it is housed in at one time. And not just access the machine at same time but also interact with each other.

But how UNIX is able to take care of different users simultaneously?

The kernel creates various processes that ultimately allows us to login. The first one is INIT process. INIT decides which of the terminals that can be used to login. The program GETTY, tells UNIX which program to execute. GETTY in turn reads data from the etc/gettydefs file, displays the login: prompt on screen and waits for input. After which it spawns the login program, which takes the login name we have keyed in as a parameter. Then INIT processes creates a child process by forking, through which login processes is executed with the help of exec() fuction.

Popularity: 4%

1. Reverse a singly linked list

//
// iterative version
//
Node* ReverseList( Node ** List )   
{
  Node *temp1 = *List;
  Node * temp2 = NULL;
  Node * temp3 = NULL;
 
  while ( temp1 )
  {
    //set the head to last node
    *List = temp1;       
 
    // save the next ptr in temp2 
    temp2= temp1->pNext; 
 
    // change next to privous
    temp1->pNext = temp3; 
    temp3 = temp1;
    temp1 = temp2;
  }
 
  return *List;
}

2. Delete a node in double linked list

void deleteNode(node *n)
{
  node *np = n->prev;
  node *nn = n->next;
  np->next = n->next;
  nn->prev = n->prev;
  delete n;
}

3. Sort a linked list

//sorting in descending order
struct node
{
  int value;
  node* NEXT;
}
//Assume HEAD pointer denotes the first 
//element in the linked list
//only change the values? don't have to 
//change the pointers
Sort( Node *Head)
{
  node* first,second,temp;
  first= Head;
  while(first!=null)
  {
    second=first->NEXT;
    while(second!=null)
    {
      if(first->value < second->value)
      {
        temp = new node();
        temp->value=first->value;
        first->value=second->value;
        second->value=temp->value;
        delete temp;
      }
      second=second->NEXT;
    }
    first=first->NEXT;
  }
}

4. Reverse a string

void ReverseString (char *String)
{
  char *Begin = String;
  char *End = String + strlen(String) - 1;
  char TempChar;
 
  while (Begin < End)
  {
    TempChar = *Begin;
    *Begin = *End;
    *End = TempChar;
    Begin++;
    End- -;
  }
}

5. Insert a node a sorted linked list

void sortedInsert(Node * head, Node* newNode)
{
  Node *current = head;
 
  // traverse the list until you find 
  //item bigger the new node value
  //   
  while ((current!= NULL) && 
         (current->data < newNode->data))
  {
    current = current->next;
  }
  //
  // insert the new node before the big item
  //
  newNode->next = current->next;
  current = newNode;
}

6. Covert a string to upper case

void ToUpper(char * S)
{
  while (*S!=0)
  {
    *S=(*S >= 'a' && *S <= 'z')?(*S-'a'+'A'):*S;
    S++;
  }
}

7. Multiple a number by 7 without using * and + operator.

// mulitplied by 2 ^ 3 = 8
NewNum = Num << 3; 
 
// 8 – 1 = 7
NewNum = NewNum - Num;

8. Write a function that takes in a string parameter and checks to see whether or not it is an integer, and if it is then return the integer value.

#include <stdio.h>
 
int strtoint(char *s)
{
  int index = 0, flag = 0;
 
  while( *(s+index) != 0)
  {
    if( (*(s + index) >= '0') && 
        *(s + index) <= '9')
    {
      flag = 1;
      index++;
    }
    else
    {
      flag = 0;
      break;
    }
  }
  if( flag == 1 )
    return atoi(s);
  else
    return 0;
}
 
main() 
{ 
  printf("%d",strtoint("0123")); 
  printf("\n%d",strtoint("0123ii")); 
}

9. Print a data from a binary tree - In-order(ascending)

//
// recursive version
//
 
Void PrintTree ( struct * node node )
{
  if ( node == NULL )
    return;
 
  PrintTree(node->left );
  printf("%d", node->data);
  PrintTree(node->right );
}

10. print integer using only putchar

//
//	recursive version
//
void PrintNum ( int Num )
{
  if ( Num == 0 )
    return;
  PrintNum ( Num / 10 );
  puthcar ( '0'+ Num % 10 );
}

11. Find the factorial of number

//
// recursive version
//
 
int Factorial( int Num )
{
  if ( num > 0 )
    return Num * Factorial ( Num –1 ); 
  else
    return 1;
}
 
//
// iterative version
//
 
int Factorial( int Num )
{
  int I
  int result = 1;
 
  for ( I= Num; I > 0; I- - )
  {
    result = result * I;
  }
 
  return result;
}

12. Generate Fib numbers:

// recursive version
int fib( n ) 
{
  if ( n < 2 )
    return 1;
  else
    return fib ( n-1 ) + fib ( n-2 );
}
 
//iterative version
int fib( n ) 
{
  int f1 =1, f2 = 1;
 
  if ( n < 2 )
    return 1;	
  for ( i = 1; i < N; i++)
  {
    f = f1 + f2;
    f1= f2;
    f = f1;
  }
  return f;
}

13. Write a function that finds the last instance of a character in a string

char *lastchar(char *String, char ch)
{
  char *pStr = NULL;
 
  // traverse the entire string
 
  while( * String ++ != NULL ) 
  {
    if( *String == ch ) 
    pStr = String;
  }
 
  return pStr;
}

14. Return Nth the node from the end of the linked list in one pass.

Node * GetNthNode ( Node* Head , int NthNode )
{
  Node * pNthNode = NULL;
  Node * pTempNode = NULL;
  int nCurrentElement = 0;
 
  for ( pTempNode = Head; 
        pTempNode != NULL; 
        pTempNode = pTempNode->pNext )
  {
    nCurrentElement++;			
    if ( nCurrentElement - NthNode == 0 )
    {
      pNthNode = Head;
    }
    else
    if ( nCurrentElement - NthNode > 0)
    {
      pNthNode = pNthNode ->pNext;
    }					
  }
  if (pNthNode )
  {
    return pNthNode;
  }
  else
    return NULL;
}

15. Counting set bits in a number.

//First version:
int CoutSetBits(int Num)
{
  for(int count=0; Num; Num >>= 1)
  {
    if (Num & 1) 
    count++;
  }
  return count;
}
 
//Optimized version:
int CoutSetBits(int Num)
{
  for(int count =0; Num; count++)
  {
    Num &= Num -1;
  }
}

Copyright
(c) 2004-2007 Satish Shetty

Popularity: 24%

C/C++ Programming interview questions and answers

By Satish Shetty

What is encapsulation?
Containing and hiding information about an object, such as internal data structures and code. Encapsulation isolates the internal complexity of an object’s operation from the rest of the application. For example, a client component asking for net revenue from a business object need not know the data’s origin.

What is inheritance?
Inheritance allows one class to reuse the state and behavior of another class. The derived class inherits the properties and method implementations of the base class and extends it by overriding methods and adding additional properties and methods.

What is Polymorphism??
Polymorphism allows a client to treat different objects in the same way even if they were created from different classes and exhibit different behaviors.

You can use implementation inheritance to achieve polymorphism in languages such as C++ and Java.

Base class object’s pointer can invoke methods in derived class objects.

You can also achieve polymorphism in C++ by function overloading and operator overloading.

What is constructor or ctor?
Constructor creates an object and initializes it. It also creates vtable for virtual functions. It is different from other methods in a class.

What is destructor?
Destructor usually deletes any extra resources allocated by the object.

What is default constructor?
Constructor with no arguments or all the arguments has default values.

What is copy constructor?
Constructor which initializes the it’s object member variables ( by shallow copying) with another object of the same class. If you don’t implement one in your class then compiler implements one for you.

for example:
Boo Obj1(10); // calling Boo constructor

Boo Obj2(Obj1); // calling boo copy constructor
Boo Obj2 = Obj1;// calling boo copy constructor

When are copy constructors called?>
Copy constructors are called in following cases:
a) when a function returns an object of that class by value
b) when the object of that class is passed by value as an argument to a function
c) when you construct an object based on another object of the same class
d) When compiler generates a temporary object

What is assignment operator?
Default assignment operator handles assigning one object to another of the same class. Member to member copy (shallow copy)

What are all the implicit member functions of the class? Or what are all the functions which compiler implements for us if we don’t define one.??

default ctor
copy ctor
assignment operator
default destructor
address operator

What is conversion constructor?
constructor with a single argument makes that constructor as conversion ctor and it can be used for type conversion.

for example:

class Boo
{
  public:
    Boo( int i );
};

Boo BooObject = 10 ; // assigning int 10 Boo object

What is conversion operator??
class can have a public method for specific data type conversions.

for example:

class Boo
{
  double value;
  public:
    Boo(int i )
    operator double()
    {
       return value;
    }
};

Boo BooObject;
double i = BooObject; // assigning object to variable i of type double.
                     //now conversion operator gets called to assign the value.

What is diff between malloc()/free() and new/delete?
malloc allocates memory for object in heap but doesn’t invoke object’s constructor to initiallize the object.

new allocates memory and also invokes constructor to initialize the object.

malloc() and free() do not support object semantics
Does not construct and destruct objects
string * ptr = (string *)(malloc (sizeof(string)))
Are not safe
Does not calculate the size of the objects that it construct
Returns a pointer to void
int *p = (int *) (malloc(sizeof(int)));
int *p = new int;
Are not extensible
new and delete can be overloaded in a class

"delete" first calls the object’s termination routine (i.e. its destructor) and then releases the space the object occupied on the heap memory. If an array of objects was created using new, then delete must be told that it is dealing with an array by preceding the name with an empty []:-

Int_t *my_ints = new Int_t[10];

…

delete []my_ints;

what is the diff between "new" and "operator new" ?

"operator new" works like malloc.

What is difference between template and macro??

There is no way for the compiler to verify that the macro parameters are of compatible types. The macro is expanded without any special type checking.

If macro parameter has a postincremented variable ( like c++ ), the increment is performed two times.

Because macros are expanded by the preprocessor, compiler error messages will refer to the expanded macro, rather than the macro definition itself. Also, the macro will show up in expanded form during debugging.

for example:

Macro:

#define min(i, j) (i < j ? i : j)

template:

template<class T> 
T min (T i, T j) 
{ 
  return i < j ? i : j;
}

What are C++ storage classes?

auto
register
static
extern

auto: the default. Variables are automatically created and initialized when they are defined and are destroyed at the end of the block containing their definition. They are not visible outside that block

register: a type of auto variable. a suggestion to the compiler to use a CPU register for performance

static: a variable that is known only in the function that contains its definition but is never destroyed and retains its value between calls to that function. It exists from the time the program begins execution

extern: a static variable whose definition and placement is determined when all object and library modules are combined (linked) to form the executable code file. It can be visible outside the file where it is defined.

What are storage qualifiers in C++ ?

They are..

const
volatile
mutable

Const keyword indicates that memory once initialized, should not be altered by a program.

volatile keyword indicates that the value in the memory location can be altered even though nothing in the program
code modifies the contents. for example if you have a pointer to hardware location that contains the time, where hardware changes the value of this pointer variable and not the program. The intent of this keyword to improve the optimization ability of the compiler.   

mutable keyword indicates that particular member of a structure or class can be altered even if a particular structure variable, class, or class member function is constant.

struct data
{
  char name[80];
  mutable double salary;
}
 
//initlized by complier
const data MyStruct = { "Satish Shetty", 1000 }; 
 
// compiler error
strcpy ( MyStruct.name, "Shilpa Shetty"); 
 
// complier is happy allowed
MyStruct.salaray = 2000 ;

What is reference ?
reference is a name that acts as an alias, or alternative name, for a previously defined variable or an object.

prepending variable with "&" symbol makes it as reference.

for example:

int a;
int &b = a;

What is passing by reference?

Method of passing arguments to a function which takes parameter of type reference.

for example:

void swap( int & x, int & y )
{
  int temp = x;
  x = y;
  y = temp;
}
 
int a=2, b=3;
swap( a, b );

Basically, inside the function there won’t be any copy of the arguments "x" and "y" instead they refer to original variables a and b. so no extra memory needed to pass arguments and it is more efficient.
 

When do use "const" reference arguments in function?
a) Using const protects you against programming errors that inadvertently alter data.
b) Using const allows function to process both const and non-const actual arguments, while a function without const in the prototype can only accept non constant arguments.
c) Using a const reference allows the function to generate and use a temporary variable appropriately.
 

When are temporary variables created by C++ compiler?
Provided that function parameter is a "const reference", compiler generates temporary variable in following 2 ways.

a) The actual argument is the correct type, but it isn’t Lvalue

double Cube(const double & num)
{
  num = num * num * num;
  return num;
}
 
double temp = 2.0;
 
//argument is a expression and not a Lvalue;
double value = cube(3.0 + temp);

b) The actual argument is of the wrong type, but of a type that can be converted to the correct type

long temp = 3L;
 
// long to double conversion 
double value = cuberoot ( temp);

What is virtual function?
When derived class overrides the base class method by redefining the same function, then if client wants to access redefined the method from derived class through a pointer from base class object, then you must define this function in base class as virtual function.

lass parent
{
  void Show() 
  { 
    cout << "i'm parent" << endl;
  }
};
 
class child: public parent
{
  void Show() 
  { 
    cout << "i'm child" << endl;
  }
};
 
parent * parent_object_ptr = new child;
 
// calls parent->show() i
parent_object_ptr->show()

now we goto virtual world…

class parent
{
  virtual void Show() 
  { 
    cout << "i'm parent" << endl;
  }
};
 
class child: public parent
{
  void Show() 
  { 
    cout << "i'm child" << endl;
  }
};
 
parent * parent_object_ptr = new child;
 
// calls child->show()
parent_object_ptr->show()

What is pure virtual function? or what is abstract class?

When you define only function prototype in a base class without implementation and do the complete implementation in derived class. This base class is called abstract class and client won’t able to instantiate an object using this base class.

You can make a pure virtual function or abstract class this way..

class Boo
{
  void foo() = 0;
}
 
Boo MyBoo; // compilation error

What is Memory alignment??

The term alignment primarily means the tendency of an address pointer value to be a multiple of some power of two. So a pointer with two byte alignment has a zero in the least significant bit. And a pointer with four byte alignment has a zero in both the two least significant bits. And so on. More alignment means a longer sequence of zero bits in the lowest bits of a pointer.

What problem does the namespace feature solve?

Multiple providers of libraries might use common global identifiers causing a name collision when an application tries to link with two or more such libraries. The namespace feature surrounds a library’s external declarations with a unique namespace that eliminates the potential for those collisions.

namespace [identifier] { namespace-body }

A namespace declaration identifies and assigns a name to a declarative region.
The identifier in a namespace declaration must be unique in the declarative region in which it is used. The identifier is the name of the namespace and is used to reference its members.

What is the use of ‘using’ declaration?

A using declaration makes it possible to use a name from a namespace without the scope operator.

What is an Iterator class?

A class that is used to traverse through the objects maintained by a container class. There are five categories of iterators: input iterators, output iterators, forward iterators, bidirectional iterators, random access. An iterator is an entity that gives access to the contents of a container object without violating encapsulation constraints. Access to the contents is granted on a one-at-a-time basis in order. The order can be storage order (as in lists and queues) or some arbitrary order (as in array indices) or according to some ordering relation (as in an ordered binary tree). The iterator is a construct, which provides an interface that, when called, yields either the next element in the container, or some value denoting the fact that there are no more elements to examine. Iterators hide the details of access to and update of the elements of a container class. Something like a pointer.

What is a dangling pointer?

A dangling pointer arises when you use the address of an object after its lifetime is over. This may occur in situations like returning addresses of the automatic variables from a function or using the address of the memory block after it is freed.

What do you mean by Stack unwinding?

It is a process during exception handling when the destructor is called for all local objects in the stack between the place where the exception was thrown and where it is caught.

Name the operators that cannot be overloaded??

sizeof, ., .*, .->, ::, ?:

What is a container class? What are the types of container classes?

A container class is a class that is used to hold objects in memory or external storage. A container class acts as a generic holder. A container class has a predefined behavior and a well-known interface. A container class is a supporting class whose purpose is to hide the topology used for maintaining the list of objects in memory. When a container class contains a group of mixed objects, the container is called a heterogeneous container; when the container is holding a group of objects that are all the same, the container is called a homogeneous container.

What is inline function??

The __inline keyword tells the compiler to substitute the code within the function definition for every instance of a function call. However, substitution occurs only at the compiler’s discretion. For example, the compiler does not inline a function if its address is taken or if it is too large to inline.
   

What is overloading??

With the C++ language, you can overload functions and operators. Overloading is the practice of supplying more than one definition for a given function name in the same scope.

- Any two functions in a set of overloaded functions must have different argument lists.
- Overloading functions with argument lists of the same types, based on return type alone, is an error.

What is Overriding?

To override a method, a subclass of the class that originally declared the method must declare a method with the same name, return type (or a subclass of that return type), and same parameter list.
The definition of the method overriding is:
Must have same method name.  
Must have same data type.  
Must have same argument list.  
Overriding a method means that replacing a method functionality in child class. To imply overriding functionality we need parent and child classes. In the child class you define the same method signature as one defined in the parent class.

What is "this" pointer?

The this pointer is a pointer accessible only within the member functions of a class, struct, or union type. It points to the object for which the member function is called. Static member functions do not have a this pointer.

When a nonstatic member function is called for an object, the address of the object is passed as a hidden argument to the function. For example, the following function call

myDate.setMonth( 3 );

can be interpreted this way:

setMonth( &myDate, 3 );

The object’s address is available from within the member function as the this pointer. It is legal, though unnecessary, to use the this pointer when referring to members of the class.

What happens when you make call "delete this;" ??

The code has two built-in pitfalls. First, if it executes in a member function for an extern, static, or automatic object, the program will probably crash as soon as the delete statement executes. There is no portable way for an object to tell that it was instantiated on the heap, so the class cannot assert that its object is properly instantiated. Second, when an object commits suicide this way, the using program might not know about its demise. As far as the instantiating program is concerned, the object remains in scope and continues to exist even though the object did itself in. Subsequent dereferencing of the pointer can and usually does lead to disaster.

You should never do this. Since compiler does not know whether the object was allocated on the stack or on the heap, "delete this" could cause a disaster.

How virtual functions are implemented C++?

Virtual functions are implemented using a table of function pointers, called the vtable.  There is one entry in the table per virtual function in the class.  This table is created by the constructor of the class.  When a derived class is constructed, its base class is constructed first which creates the vtable.  If the derived class overrides any of the base classes virtual functions, those entries in the vtable are overwritten by the derived class constructor.  This is why you should never call virtual functions from a constructor: because the vtable entries for the object may not have been set up by the derived class constructor yet, so you might end up calling base class implementations of those virtual functions

What is name mangling in C++??

The process of encoding the parameter types with the function/method name into a unique name is called name mangling. The inverse process is called demangling.

For example Foo::bar(int, long) const is mangled as `bar__C3Fooil’.
For a constructor, the method name is left out. That is Foo::Foo(int, long) const is mangled as `__C3Fooil’.

What is the difference between a pointer and a reference?

A reference must always refer to some object and, therefore, must always be initialized; pointers do not have such restrictions. A pointer can be reassigned to point to different objects while a reference always refers to an object with which it was initialized.

How are prefix and postfix versions of operator++() differentiated?

The postfix version of operator++() has a dummy parameter of type int. The prefix version does not have dummy parameter.

What is the difference between const char *myPointer and char *const myPointer?

Const char *myPointer is a non constant pointer to constant data; while char *const myPointer is a constant pointer to non constant data.

How can I handle a constructor that fails?

throw an exception. Constructors don’t have a return type, so it’s not possible to use return codes. The best way to signal constructor failure is therefore to throw an exception.

How can I handle a destructor that fails?

Write a message to a log-file. But do not throw an exception.
The C++ rule is that you must never throw an exception from a destructor that is being called during the "stack unwinding" process of another exception. For example, if someone says throw Foo(), the stack will be unwound so all the stack frames between the throw Foo() and the } catch (Foo e) { will get popped. This is called stack unwinding.
During stack unwinding, all the local objects in all those stack frames are destructed. If one of those destructors throws an exception (say it throws a Bar object), the C++ runtime system is in a no-win situation: should it ignore the Bar and end up in the } catch (Foo e) { where it was originally headed? Should it ignore the Foo and look for a } catch (Bar e) { handler? There is no good answer — either choice loses information.
So the C++ language guarantees that it will call terminate() at this point, and terminate() kills the process. Bang you’re dead.

What is Virtual Destructor?

Using virtual destructors, you can destroy objects without knowing their type - the correct destructor for the object is invoked using the virtual function mechanism. Note that destructors can also be declared as pure virtual functions for abstract classes.

if someone will derive from your class, and if someone will say "new Derived", where "Derived" is derived from your class, and if someone will say delete p, where the actual object’s type is "Derived" but the pointer p’s type is your class.

 
Can you think of a situation where your program would crash without reaching the breakpoint which you set at the beginning of main()?

C++ allows for dynamic initialization of global variables before main() is invoked. It is possible that initialization of global will invoke some function. If this function crashes the crash will occur before main() is entered.

Name two cases where you MUST use initialization list as opposed to assignment in constructors.

Both non-static const data members and reference data members cannot be assigned values; instead, you should use initialization list to initialize them.

Can you overload a function based only on whether a parameter is a value or a reference?

No. Passing by value and by reference looks identical to the caller.

What are the differences between a C++ struct and C++ class?

The default member and base class access specifiers are different.

The C++ struct has all the features of the class. The only differences are that a struct defaults to public member access and public base class inheritance, and a class defaults to the private access specifier and private base class inheritance.

What does extern "C" int func(int *, Foo) accomplish?

It will turn off "name mangling" for func so that one can link to code compiled by a C compiler.

How do you access the static member of a class?

<ClassName>::<StaticMemberName>

What is multiple inheritance(virtual inheritance)? What are its advantages and disadvantages?

Multiple Inheritance is the process whereby a child can be derived from more than one parent class. The advantage of multiple inheritance is that it allows a class to inherit the functionality of more than one base class thus allowing for modeling of complex relationships. The disadvantage of multiple inheritance is that it can lead to a lot of confusion(ambiguity) when two base classes implement a method with the same name.

What are the access privileges in C++? What is the default access level?

The access privileges in C++ are private, public and protected. The default access level assigned to members of a class is private. Private members of a class are accessible only within the class and by friends of the class. Protected members are accessible by the class itself and it’s sub-classes. Public members of a class can be accessed by anyone.

What is a nested class? Why can it be useful?
A nested class is a class enclosed within the scope of another class. For example:

//Example 1: Nested class
//
class OuterClass
{
  class NestedClass
  {
    // ...
  };
  // ...
};

Nested classes are useful for organizing code and controlling access and dependencies. Nested classes obey access rules just like other parts of a class do; so, in Example 1, if NestedClass is public then any code can name it as OuterClass::NestedClass. Often nested classes contain private implementation details, and are therefore made private; in Example 1, if NestedClass is private, then only OuterClass’s members and friends can use NestedClass.

When you instantiate as outer class, it won’t instantiate inside class.

What is a local class? Why can it be useful?
local class is a class defined within the scope of a function — any function, whether a member function or a free function. For example:

//Example 2: Local class
//
int f()
{
  class LocalClass
  {
    // ...
  };
  // ...
};

Like nested classes, local classes can be a useful tool for managing code dependencies.

Can a copy constructor accept an object of the same class as parameter, instead of reference of the object?
 

No. It is specified in the definition of the copy constructor itself. It should generate an error if a programmer specifies a copy constructor with a first argument that is an object and not a reference.

copyright (c) 2004-2007, Satish Shetty, All rights reserved,

Popularity: 76%

To calculate the size of an object, we need the type information.
This type information is available only at compile time.  At the
end of the compilation phase, the resulting object code doesn’t
have (or not required to have) the type information.

Of course, type information can be stored to access it at run-time,
but this results in bigger object code and less performance.  And
most of the time, we don’t need it.

All the runtime environments that support run time type
identification (RTTI) will retain type information even after
compilation phase.  And if, something can be done in compilation
time itself, why do it at run time?

More importantly, HOW can it be a function when the operand is a
type, not an expression. Even expressions subject to integral
promotion are problematic.

Popularity: 7%

    Following are few differece in C and C++.  Few of these are allowed in
C++, but with a different meaning; while some are illegal.

1.  sizeof (’1′) == sizeof (int) in C; but it is sizeof (char) in C++.

2.  You generally should NOT use *alloc()/free() in C++; but they are the
    only such functions in C.  Use new and delete combination, instead.

3.  Functions need not be prototyped in C; but, it’s a must in C++.
    Peter Nilsson says:

       "C99 changed from C90 in that named functions must be _declared_ prior
        to usage, but there is still no requirement that the function be
        prototyped. [The exception being variadic functions like printf,
        which have always required prototypes in standard C.]"

4.  struct a {
        struct b {
            int a;
        };
    };

    struct b b;         /* allowed in C; but, not in C++ */

5.  const int b = 1;    /* allowed in C and C++ */
    const int a;        /* allowed in C, but not in C++ */

6.  Global variables can be defined more than once in C, not in C++.
    int a;              /* both in C and C++ */
    int a = 10;         /* legal in C; illegal in C++ */

7.  const a;            /* allowed in C; illegal in C++ */

    This is equivalent to const int a; in C.

8.  char s[7] = "vijoeyz";  /* error in C++, but allowed in C */

9.  K&R style function definitions are not allowed in C++.  Example:

    void mango ( a )
    int a;
    {   …  }

Popularity: 6%

Linked Lists Basics
[Download this tutorial as , for updated conetnt and comments, generate a new pdf with the option which is present below the post] 

What are Linked Lists?
Linked lists store collections of data like arrays.  Linked lists are chain of records/nodes, one record/node points to the next. Record holds the data.

Why Linked Lists?
There are several  disadvantages with arrays, here are some…
1) The size of the array is fixed. Most often this size is specified at compile time however the size of the array can be deferred until the array is created at runtime (from heap), but after that it remains fixed. This causes to waste memory eventhough e may not use.
2) Inserting new elements at the front is potentially expensive because existing elements need to be shifted over to make room.
3)When array was full, to insert more data, it need to be resized, this operation is quite expensive, even may not be possible if in case memory got fragmented.
Linked lists performs well where arrays fail to do it.

What Linked Lists Look Like
An array allocates memory for all its elements lumped together as one block of memory. In contrast, a linked list allocates space for each element separately in its own block of memory called a "linked list element" or "node". The list gets is overall structure by using pointers to connect all its nodes together like the links in a chain. Each node contains two fields: a "data" field to store whatever element type the list holds for its client, and a "next" field which is a pointer used to link one node to the next node. Here is the graphical representation of linked list in fig1.

 

Empty Linked List
Empty list contains no nodes. The most common representation for the empty list is a NULL head pointer.

Linked List Type:
As we have discussed already linked list is chain of nodes. A node is a strcutre which holds data and pointer to the next node
Here is C structure for a node:

struct Node
{
  void* info; //data
  Node* next; //used to point to next node
};

Implementation Variants
There are a many variations on the basic linked list which have individual advantages over the basic linked list.
Without Special Nodes this implementation doesn’t use any special (head/dummy) nodes, empty list representation of this type of implementation is NULL. The advantage of this variant is, it doesn’t waste meory (it uses  all nodes), on other hand it complicates operations on lists a bit.
Head pointer in this implementation, we choose as a representation of the empty list a single "dummy" node whose .data field is unused. We call this node as head. The advantage of this technique is that it makes operations on the list easy on the other hand it wastes a node without using it.
Tail Pointer The list is not represented by a single head pointer. Instead the list is represented by a head pointer which points to the first node and a tail pointer which points to the last node. The tail pointer allows operations at the end of the list such as adding an end element or appending two lists to work efficiently.
Circular Instead of setting the .next field of the last node to NULL, set it to point back around to the first node. Instead of needing a fixed head end, any pointer into the list will do.
Doubly-Linked Instead of just a single .next field, each node incudes both .next and .previous pointers. Insertion and deletion now require more operations. but other operations are simplified. Given a pointer to a node, insertion and deletion can be performed directly whereas in the singly linked case, the iteration typically needs to locate the point just before the point of change in the list so the .next pointers can be followed downstream.
Circular  Doubly-Linked Instead of setting the .next field of the last node to NULL and .prev field of first node to NULL, set last node to point back around to the first node and first node .prev points to last node. This even simplifies and enhance efficiency of some operations doubly linked list.
Chunk List Instead of storing a single client element in each node, store a little constant size array of client elements in each node. Tuning the number of elements per node can provide different performance characteristics: many elements per node has performance more like an array, few elements per node has performance more like a linked list. The Chunk List is a good way to build a linked list with good performance.
Dynamic Array Instead of using a linked list, elements may be stored in an array block allocated in the heap. It is possible to grow and shrink the size of the block as needed with calls to the system function realloc(). Managing a heap block in this way is a fairly complex, but can have excellent efficiency for storage and iteration., especially because modern memory systems are tuned for the access of contiguous areas of memory. In contrast, linked list can actually be a little inefficient, since they tend to iterate through memory areas that are not adjacent.

Advantages and Disadvantages
Arrays:
1)Accessing/Searching : fast due to random access of any element in array (remember address of array element will be computed as base address + offset, so its just memory fetch along with one addition operation) — O(1)
2)Inserting/Deleting at end — fast — O(1)
3)Even sequential access on arrays are fast — due to locality of reference, for linked lists this may not well applied
1) The size of the array is fixed. Most often this size is specified at compile time however the size of the array can be deferred until the array is created at runtime (from heap), but after that it remains fixed. This causes to waste memory eventhough e may not use.
2) Inserting/Deleting  elements at the front is potentially expensive because existing elements need to be shifted over to make room — O(n)
3)When array was full, to insert more data, it need to be resized, this operation is quite expensive, even may not be possible if in case memory got fragmented.
Linked lists performs well where arrays fail to do it.
Linked Lists:
1)Accessing/Searching: sequential access -  O(n)
2)Inserting/Deleting at the end — fast — O(1)
3)Inserting/Deleting at the beginning — fast — O(1)
4)It makes good persistent data structure (because two or more lists can have a common tail, so several versions of a data can be maintained, new data comes at the beginning of a new list)
5)No space problems, memory effectively used.
6)Inserting/Deleting in the middle — O(n)
7)can not make use of locality of reference

Double Linked Lists:
1)More space for node
2)Complicates basic operations like insertion and deletion, however inserting/deleting any node will done in constant number of operations given that node address — O(1).
3)manipulating nodes are easy because provides access from both sides of the list
4)do not allow tail sharing, so can not be used as persistent data structures

Circular Linked Lists & Circular Double Linked Lists:
1)Can be traversed anywhere given any node in the list, which gives flexibility
2)Enahnces efficiencies of some operations
3)Complicates operations by inducing special cases to deal with circularity of list

Operations on Linked Lists:
Inserting node:

A node can inserted if we know the previous node’s address. Previous node’s next pointer altered to point to new node, new node’s next pointer points previous node’s next node.

//insert after a known node and return the inserted node
Node *insert(Node *after, void *data)
{
  Node* n;
  n = (Node *) malloc (sizeof(Node));
  n->info = data;
 
  //incase header node is not created
  if (!after)
  {
    n->next = after;
    return n;
  }
 
  n->next = after->next;
  after->next = n;
 
  return n;
}

Complexity: O(n)
Special Cases: inserting at beginning: O(1)

Deleting Node:

A node can deleted if we know the previous node’s address. Previous node’s next pointer altered to point to next next node, and previous node’s next node memory will be freed.

//delete after a known node and return the node after deleted node
Node *delete(Node *after)
{
  Node* tmp;
 
  if (!after || !(a