Source Code for Tree Traversal

Source Code for String Reversing

Data Structures

Arrays is a data structure that is uesd more than any other data structure , They are simple to use but have typical problems leading to serious issues.More...

Linked List This provide dynamic growing of Data, Data is represented as a chain of nodes. Each node is having data and a link to next nodeMore.....

Trees contains nodes which are represented as roots and child nodes. Just like parental hiararchy. Variations of trees are like binary trees, AVL, RedBlakMore....

Stack is a data structure which can be visualized as a stack of disks where items can be inserted one above another. The basic rule is the item which is placed first will be removed last and vice versaMore....

Basic Data Structure Interview Questions And Answers
 

How is any Data Structure application is classified among files?">How is any Data Structure application is classified among files?

A linked list application can be organized into a header file, source file and main application file. The first file is the header file that contains the definition of the NODE structure and the LinkedList class definition. The second file is a source code file containing the implementation of member functions of the LinkedList class. The last file is the application file that contains code that creates and uses the LinkedList class.

Link to What member function places a new node at the end of the linked list?">What member function places a new node at the end of the linked list?

The appendNode() member function places a new node at the end of the linked list. The appendNode() requires an integer representing the current data of the node.

What is Linked List ?

Linked List is one of the fundamental data structures. It consists of a sequence of nodes, each containing arbitrary data fields and one or two (”links”) pointing to the next and/or previous nodes. A linked list is a self-referential datatype because it contains a pointer or link to another data of the same type. Linked lists permit insertion and removal of nodes at any point in the list in constant time, but do not allow random access.

What does each entry in the Link List called?

Each entry in a linked list is called a node. Think of a node as an entry that has three sub entries. One sub entry contains the data, which may be one attribute or many attributes. Another points to the previous node, and the last points to the next node. When you enter a new item on a linked list, you allocate the new node and then set the pointers to previous and next nodes.

How is the front of the queue calculated ?

The front of the queue is calculated by front = (front+1) % size.

Why is the isEmpty() member method called?

The isEmpty() member method is called within the dequeue process to determine if there is an item in the queue to be removed i.e. isEmpty() is called to decide whether the queue has at least one element. This method is called by the dequeue() method before returning the front element.


Which process places data at the back of the queue?

Enqueue is the process that places data at the back of the queue.

What is the relationship between a queue and its underlying array?

Data stored in a queue is actually stored in an array. Two indexes, front and end will be used to identify the start and end of the queue.

When an element is removed front will be incremented by 1. In case it reaches past the last index available it will be reset to 0. Then it will be checked with end. If it is greater than end queue is empty.

When an element is added end will be incremented by 1. In case it reaches past the last index available it will be reset to 0. After incrementing it will be checked with front. If they are equal queue is full.

What is a queue ?

A Queue is a sequential organization of data. A queue is a first in first out type of data structure. An element is inserted at the last position and an element is always taken out from the first position.

What does isEmpty() member method determines?

isEmpty() checks if the stack has at least one element. This method is called by Pop() before retrieving and returning the top element.

What method removes the value from the top of a stack?

The pop() member method removes the value from the top of a stack, which is then returned by the pop() member method to the statement that calls the pop() member method.

What method is used to place a value onto the top of a stack?

push() method, Push is the direction that data is being added to the stack. push() member method places a value onto the top of a stack.

Run Time Memory Allocation is known as….

Allocating memory at runtime is called a dynamically allocating memory. In this,you dynamically allocate memory by using the new operator when declaring the array, for example:int grades[] = new int[10];

How do you assign an address to an element of a pointer array ?

We can assign a memory address to an element of a pointer array by using the address operator, which is the ampersand (&), in an assignment statement such as ptemployee[0] = &projects[2];

Why do we Use a Multidimensional Array?

A multidimensional array can be useful to organize subgroups of data within an array. In addition to organizing data stored in elements of an array, a multidimensional array can store memory addresses of data in a pointer array and an array of pointers.

Multidimensional arrays are used to store information in a matrix form.
e.g. a railway timetable, schedule cannot be stored as a single dimensional array.
One can use a 3-D array for storing height, width and length of each room on each floor of a building.

What is significance of ” * ” ?

The symbol “*” tells the computer that you are declaring a pointer.
Actually it depends on context.
In a statement like int *ptr; the ‘*’ tells that you are declaring a pointer.
In a statement like int i = *ptr; it tells that you want to assign value pointed to by ptr to variable i.

The symbol “*” is also called as Indirection Operator/ Dereferencing Operator

What is Data Structure?

A data structure is a group of data elements grouped together under one name. These data elements, known as members, can have different types and different lengths. Some are used to store the data of same type and some are used to store different types of data.

Is Pointer a variable?

Yes, a pointer is a variable and can be used as an element of a structure and as an attribute of a class in some programming languages such as C++, but not Java. However, the contents of a pointer is a memory address of another location of memory, which is usually the memory address of another variable, element of a structure, or attribute of a class.

How many parts are there in a declaration statement?

There are two main parts, variable identifier and data type and the third type is optional which is type qualifier like signed/unsigned.

How memory is reserved using a declaration statement ?

Memory is reserved using data type in the variable declaration. A programming language implementation has predefined sizes for its data types.

For example, in C# the declaration int i; will reserve 32 bits for variable i.

A pointer declaration reserves memory for the address or the pointer variable, but not for the data that it will point to. The memory for the data pointed by a pointer has to be allocated at runtime.

What is impact of signed numbers on the memory?

Sign of the number is the first bit of the storage allocated for that number. So you get one bit less for storing the number. For example if you are storing an 8-bit number, without sign, the range is 0-255. If you decide to store sign you get 7 bits for the number plus one bit for the sign. So the range is -128 to +127

What is precision?

Precision refers the accuracy of the decimal portion of a value. Precision is the number of digits allowed after the decimal point.

What is the difference bitween NULL AND VOID pointer?

NULL can be value for pointer type variables.
VOID is a type identifier which has not size.
NULL and void are not same. Example: void* ptr = NULL;

What is the difference between ARRAY and STACK?

STACK follows LIFO. Thus the item that is first entered would be the last removed.

In array the items can be entered or removed in any order. Basically each member access is done using index. No strict order is to be followed here to remove a particular element.

Tell how to check whether a linked list is circular.

Create two pointers, each set to the start of the list. Update each as follows:

while (pointer1)

{
pointer1 = pointer1->next;
pointer2 = pointer2->next; if (pointer2) pointer2=pointer2->next;
if (pointer1 == pointer2)

{
print (\”circular\n\”);
}
}

Whether Linked List is linear or Non-linear data structure?

According to Access strategies Linked list is a linear one.

According to Storage Linked List is a Non-linear one

What is the data structures used to perform recursion?

Stack. Because of its LIFO (Last In First Out) property it remembers its ‘caller’ so knows whom to return when the function has to return. Recursion makes use of system stack for storing the return addresses of the function calls.Every recursive function has its equivalent iterative (non-recursive) function. Even when such equivalent iterative procedures are written, explicit stack is to be used.

If you are using C language to implement the heterogeneous linked list, what pointer type will you use?

The heterogeneous linked list contains different data types in its nodes and we need a link, pointer to connect them. It is not possible to use ordinary pointers for this. So we go for void pointer. Void pointer is capable of storing pointer to any type as it is a generic pointer type.

List out the areas in which data structures are applied extensively?

Ø Compiler Design,

Ø Operating System,

Ø Database Management System,

Ø Statistical analysis package,

Ø Numerical Analysis,

Ø Graphics,

Ø Artificial Intelligence,

Ø Simulation

What is placement new?

When you want to call a constructor directly, you use the placement new. Sometimes you have some raw memory that’s already been allocated, and you need to construct an object in the memory you have. Operator new’s special version placement new allows you to do it.
class Widget
{
public :
Widget(int widgetsize);

Widget* Construct_widget_int_buffer(void *buffer,int widgetsize)
{
return new(buffer) Widget(widgetsize);
}
};
This function returns a pointer to a Widget object that’s constructed within the buffer passed to the function. Such a function might be useful for applications using shared memory or memory-mapped I/O, because objects in such applications must be placed at specific addresses or in memory allocated by special routines.

When can you tell that a memory leak will occur?

A memory leak occurs when a program loses the ability to free a block of dynamically allocated memory.

What is a node class?

A node class is a class that, relies on the base class for services and implementation, provides a wider interface to te users than its base class, relies primarily on virtual functions in its public interface depends on all its direct and indirect base class can be understood only in the context of the base class can be used as base for further derivation
can be used to create objects. A node class is a class that has added new services or functionality beyond the services inherited from its base class.

How many different trees are possible with 10 nodes ?

1014 - For example, consider a tree with 3 nodes(n=3), it will have the maximum combination of 5 different (ie, 23 - 3 = 5) trees.

Minimum number of queues needed to implement the priority queue?

Two. One queue is used for actual storing of data and another for storing priorities.

In an AVL tree, at what condition the balancing is to be done?

If the ‘pivotal value’ (or the ‘Height factor’) is greater than 1 or less than –1.

What is the bucket size, when the overlapping and collision occur at same time?

One. If there is only one entry possible in the bucket, when the collision occurs, there is no way to accommodate the colliding value. This results in the overlapping of values.


What is the easiest sorting method to use?

The answer is the standard library function qsort(). It’s the easiest sort by far for several reasons:
It is already written.
It is already debugged.

It has been optimized as much as possible (usually).
Void qsort(void *buf, size_t num, size_t size, int (*comp)(const void *ele1, const void *ele2));

What is the heap?

The heap is where malloc(), calloc(), and realloc() get memory.

Getting memory from the heap is much slower than getting it from the stack. On the other hand, the heap is much more flexible than the stack. Memory can be allocated at any time and deallocated in any order. Such memory isn’t deallocated automatically; you have to call free().
Recursive data structures are almost always implemented with memory from the heap. Strings often come from there too, especially strings that could be very long at runtime. If you can keep data in a local variable (and allocate it from the stack), your code will run faster than if you put the data on the heap. Sometimes you can use a better algorithm if you use the heap—faster, or more robust, or more flexible. It’s a tradeoff.
If memory is allocated from the heap, it’s available until the program ends. That’s great if you remember to deallocate it when you’re done. If you forget, it’s a problem. A “memory leak” is some allocated memory that’s no longer needed but isn’t deallocated. If you have a memory leak inside a loop, you can use up all the memory on the heap and not be able to get any more. (When that happens, the allocation functions return a null pointer.) In some environments, if a program doesn’t deallocate everything it allocated, memory stays unavailable even after the program ends.

How can I search for data in a linked list?

Unfortunately, the only way to search a linked list is with a linear search, because the only way a linked list’s members can be accessed is sequentially. Sometimes it is quicker to take the data from a linked list and store it in a different data structure so that searches can be more efficient.

What is the quickest sorting method to use?

The answer depends on what you mean by quickest. For most sorting problems, it just doesn’t matter how quick the sort is because it is done infrequently or other operations take significantly more time anyway. Even in cases in which sorting speed is of the essence, there is no one answer. It depends on not only the size and nature of the data, but also the likely order. No algorithm is best in all cases.There are three sorting methods in this author’s “toolbox” that are all very fast and that are useful in different situations. Those methods are quick sort, merge sort, and radix sort.

The Quick Sort

The quick sort algorithm is of the “divide and conquer” type. That means it works by reducing a sorting
problem into several easier sorting problems and solving each of them. A “dividing” value is chosen from the input data, and the data is partitioned into three sets: elements that belong before the dividing value, the value itself, and elements that come after the dividing value. The partitioning is performed by exchanging elements that are in the first set but belong in the third with elements that are in the third set but belong in the first Elements that are equal to the dividing element can be put in any of the three sets—the algorithm will still work properly.

The Merge Sort
The merge sort is a “divide and conquer” sort as well. It works by considering the data to be sorted as a
sequence of already-sorted lists (in the worst case, each list is one element long). Adjacent sorted lists are merged into larger sorted lists until there is a single sorted list containing all the elements. The merge sort is good at sorting lists and other data structures that are not in arrays, and it can be used to sort things that don’t fit into memory. It also can be implemented as a stable sort.

The Radix Sort
The radix sort takes a list of integers and puts each element on a smaller list, depending on the value of its least significant byte. Then the small lists are concatenated, and the process is repeated for each more significant byte until the list is sorted. The radix sort is simpler to implement on fixed-length data such as ints.

Does the minimum spanning tree of a graph give the shortest distance between any 2 specified nodes?

Minimal spanning tree assures that the total weight of the tree is kept at its minimum. But it doesn’t mean that the distance between any two nodes involved in the minimum-spanning tree is minimum.

What is a spanning Tree?

A spanning tree is a tree associated with a network. All the nodes of the graph appear on the tree once. A minimum spanning tree is a spanning tree organized so that the total edge weight between nodes is minimized.

In RDBMS, what is the efficient data structure used in the internal storage representation?

B+ tree. Because in B+ tree, all the data is stored only in leaf nodes, that makes searching easier. This corresponds to the records that shall be stored in leaf nodes.

List out few of the Application of tree data-structure?

The manipulation of Arithmetic expression,Symbol Table construction,Syntax analysis.

What are the methods available in storing sequential files ?

Straight merging,Natural merging,Polyphase sort,Distribution of Initial runs.

What is the data structures used to perform recursion?

Stack. Because of its LIFO (Last In First Out) property it remembers its ‘caller’ so knows whom to return when the function has to return. Recursion makes use of system stack for storing the return addresses of the function calls.Every recursive function has its equivalent iterative (non-recursive) function. Even when such equivalent iterative procedures are written, explicit stack is to be used.

If you are using C language to implement the heterogeneous linked list, what pointer type will you use?

The heterogeneous linked list contains different data types in its nodes and we need a link, pointer to connect them. It is not possible to use ordinary pointers for this. So we go for void pointer. Void pointer is capable of storing pointer to any type as it is a generic pointer type.

List out the areas in which data structures are applied extensively?

Compiler Design,,Operating System,Database Management System,Statistical analysis package,Numerical Analysis,Graphics,Artificial Intelligence,Simulation

1. If you are using C language to implement the heterogeneous linked list, what pointer type will you use?
The heterogeneous linked list contains different data types in its nodes and we need a link, pointer to connect them. It is not possible to use ordinary pointers for this. So we go for void pointer. Void pointer is capable of storing pointer to any type as it is a generic pointer type.

2. Minimum number of queues needed to implement the priority queue?
Two. One queue is used for actual storing of data and another for storing priorities.

3. What is the data structures used to perform recursion?
Stack. Because of its LIFO (Last In First Out) property it remembers its ‘caller’ so knows whom to return when the function has to return. Recursion makes use of system stack for storing the return addresses of the function calls.
Every recursive function has its equivalent iterative (non-recursive) function. Even when such equivalent iterative procedures are written, explicit stack is to be used.

4. What are the notations used in Evaluation of Arithmetic Expressions using prefix and postfix forms?
Polish and Reverse Polish notations.

5. Convert the expression ((A + B) * C – (D – E) ^ (F + G)) to equivalent Prefix and Postfix notations.
Prefix Notation:
^ - * +ABC - DE + FG
Postfix Notation:
AB + C * DE - - FG + ^

6. Sorting is not possible by using which of the following methods?
(a) Insertion
(b) Selection
(c) Exchange
(d) Deletion

(d) Deletion.
Using insertion we can perform insertion sort, using selection we can perform selection sort, using exchange we can perform the bubble sort (and other similar sorting methods). But no sorting method can be done just using deletion.

8. What are the methods available in storing sequential files ?
 Straight merging,
 Natural merging,
 Polyphase sort,
 Distribution of Initial runs.

10. List out few of the Application of tree data-structure?
 The manipulation of Arithmetic expression,
 Symbol Table construction,
 Syntax analysis.

11. List out few of the applications that make use of Multilinked Structures?
 Sparse matrix,
 Index generation.

12. In tree construction which is the suitable efficient data structure?
(a) Array (b) Linked list (c) Stack (d) Queue (e) none

(b) Linked list

13. What is the type of the algorithm used in solving the 8 Queens problem?
Backtracking

14. In an AVL tree, at what condition the balancing is to be done?
If the ‘pivotal value’ (or the ‘Height factor’) is greater than 1 or less than –1.

15. What is the bucket size, when the overlapping and collision occur at same time?
One. If there is only one entry possible in the bucket, when the collision occurs, there is no way to accommodate the colliding value. This results in the overlapping of values.

24. Classify the Hashing Functions based on the various methods by which the key value is found.
 Direct method,
 Subtraction method,
 Modulo-Division method,
 Digit-Extraction method,
 Mid-Square method,
 Folding method,
 Pseudo-random method.

25. What are the types of Collision Resolution Techniques and the methods used in each of the type?
 Open addressing (closed hashing),
The methods used include:
Overflow block,
 Closed addressing (open hashing)
The methods used include:
Linked list,
Binary tree…

26. In RDBMS, what is the efficient data structure used in the internal storage representation?
B+ tree. Because in B+ tree, all the data is stored only in leaf nodes, that makes searching easier. This corresponds to the records that shall be stored in leaf nodes.

27. Draw the B-tree of order 3 created by inserting the following data arriving in sequence – 92 24 6 7 11 8 22 4 5 16 19 20 78

28. Of the following tree structure, which is, efficient considering space and time complexities?
(a) Incomplete Binary Tree
(b) Complete Binary Tree
(c) Full Binary Tree

(b) Complete Binary Tree.
By the method of elimination:
Full binary tree loses its nature when operations of insertions and deletions are done. For incomplete binary trees, extra storage is required and overhead of NULL node checking takes place. So complete binary tree is the better one since the property of complete binary tree is maintained even after operations like additions and deletions are done on it.

29. What is a spanning Tree?
A spanning tree is a tree associated with a network. All the nodes of the graph appear on the tree once. A minimum spanning tree is a spanning tree organized so that the total edge weight between nodes is minimized.

30. Does the minimum spanning tree of a graph give the shortest distance between any 2 specified nodes?
No.
Minimal spanning tree assures that the total weight of the tree is kept at its minimum. But it doesn’t mean that the distance between any two nodes involved in the minimum-spanning tree is minimum.

32. Which is the simplest file structure?
(a) Sequential
(b) Indexed
(c) Random

(a) Sequential

33. Whether Linked List is linear or Non-linear data structure?
According to Access strategies Linked list is a linear one.
According to Storage Linked List is a Non-linear one.

35. For the following COBOL code, draw the Binary tree?

01 STUDENT_REC.
02 NAME.
03 FIRST_NAME PIC X(10).
03 LAST_NAME PIC X(10).

02 YEAR_OF_STUDY.
03 FIRST_SEM PIC XX.
03 SECOND_SEM PIC XX.

What is a data structure?

What does abstract data type means?

Evaluate the following prefix expression " ++ 26 + - 1324" (Similar types can be asked)

Convert the following infix expression to post fix notation ((a+2)*(b+4)) -1 (Similar types can be asked)

How is it possible to insert different type of elements in stack?

Stack can be described as a pointer. Explain.

Write a Binary Search program

Write programs for Bubble Sort, Quick sort

Explain about the types of linked lists

How would you sort a linked list?

Write the programs for Linked List (Insertion and Deletion) operations

What data structure would you mostly likely see in a non recursive implementation of a recursive algorithm?

What do you mean by Base case, Recursive case, Binding Time, Run-Time Stack and Tail Recursion?

Explain quick sort and merge sort algorithms and derive the time-constraint relation for these.

Explain binary searching, Fibinocci search.

What is the maximum total number of nodes in a tree that has N levels? Note that the root is level (zero)

How many different binary trees and binary search trees can be made from three nodes that contain the key values 1, 2 & 3?

A list is ordered from smaller to largest when a sort is called. Which sort would take the longest time to execute?

A list is ordered from smaller to largest when a sort is called. Which sort would take the shortest time to execute?

When will you sort an array of pointers to list elements, rather than sorting the elements themselves?

The element being searched for is not found in an array of 100 elements. What is the average number of comparisons needed in a sequential search to determine that the element is not there, if the elements are completely unordered?

What is the average number of comparisons needed in a sequential search to determine the position of an element in an array of 100 elements, if the elements are ordered from largest to smallest?

Which sort show the best average behavior?

What is the average number of comparisons in a sequential search?

Which data structure is needed to convert infix notations to post fix notations?

What do you mean by:

Syntax Error

Logical Error

Runtime Error

How can you correct these errors?

In which data structure, elements can be added or removed at either end, but not in the middle?

How will inorder, preorder and postorder traversals print the elements of a tree?

Parenthesis are never needed in prefix or postfix expressions. Why?

Which one is faster? A binary search of an orderd set of elements in an array or a sequential search of the elements.