Data Structure Interview questions with answers
Latest answer: The scheme of organizing related information is
known as ‘data structure’. The types of data structure are: Lists:
A group of similar items with connectivity to the previous or/and next data
items.................
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Latest answer: Linear data structure: A linear data structure
traverses the data elements sequentially, in which only one data element can
directly be reached. Ex: Arrays, Linked Lists...............
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answer
Latest answer: An array is a set of homogeneous elements. Every
element is referred by an index.
Arrays are used for storing the data until the application expires in the main
memory of the computer system. So that, the elements can be accessed at any
time. The operations are:
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Latest answer: A matrix is a representation of certain rows and
columns, to persist homogeneous data. It can also be called as
double-dimensioned array.................
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Latest answer: Algorithm: A step by step process to get the
solution for a well defined problem..............
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answer
Latest answer: The process of attempting for solving a problem
which finds successive approximations for solution, starting from an initial
guess.............
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Latest answer: Recursive algorithm is a method of
simplification that divides the problem into sub-problems of the same nature.
The result of one recursion is the input for the next recursion...............
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Latest answer: In Huffman Algorithm, a set of nodes assigned
with values if fed to the algorithm................
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Latest answer: Quick sort employs the ‘divide and conquer’
concept by dividing the list of elements into two sub elements............
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answer
Latest answer: Bubble Sort: The simplest sorting algorithm. It
involves the sorting the list in a repetitive fashion. It compares two adjacent
elements in the list..............
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Latest answer: Stack – Represents the collection of elements in
Last In First Out order.
Operations includes testing null stack, finding the top element in the stack,
removal of top most element and adding elements on the top of the
stack..............
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Latest answer: A stack is represented as a pointer. The reason
is that, it has a head pointer which points to the top of the
stack..............
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Latest answer: Recursion is an approach in which a function
calls itself with an argument. Upon reaching a termination condition, the
control returns to the calling function...............
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Latest answer: Different elements can be inserted into a stack.
This is possible by implementing union / structure data type............
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answer
Latest answer: A linked list is a dynamic data structure. It
consists of a sequence of data elements and a reference to the next record in
the sequence. Stacks, queues, hash tables, linear equations, prefix and post
fix operations..................
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answer
Latest answer: The types of linked lists are:
Singly linked list: It has only head part and corresponding references to the
next nodes...............
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answer
Latest answer: Step 1: Compare the current node in the unsorted
list with every element in the rest of the list. If the current element is more
than any other element go to step 2 otherwise go to step 3..............
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Latest answer: Sequential search: Searching an element in an
array, the search starts from the first element till the last
element..............
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Latest answer: Binary Search: Binary search is the process of
locating an element in a sorted list. The search starts by dividing the list
into two parts...............
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answer
Data Structure interview - posted on September 30, 2009 at 15:50 AM
by Vidya Sagar
What is a data structure? What are the types of data structures? Briefly
explain them
The scheme of organizing related information is known as ‘data structure’. The
types of data structure are:
Lists: A group of similar items with connectivity to the
previous or/and next data items.
Arrays: A set of homogeneous values
Records: A set of fields, where each field consists of data belongs to one data
type.
Trees: A data structure where the data is organized in a
hierarchical structure. This type of data structure follows the sorted order of
insertion, deletion and modification of data items.
Tables: Data is persisted in the form of rows and columns.
These are similar to records, where the result or manipulation of data is
reflected for the whole table.
Define a linear and non linear data structure.
Linear data structure: A linear data structure traverses the
data elements sequentially, in which only one data element can directly be
reached. Ex: Arrays, Linked Lists
Non-Linear data structure: Every data item is attached to
several other data items in a way that is specific for reflecting
relationships. The data items are not arranged in a sequential structure. Ex:
Trees, Graphs
Define in brief an array. What are the types of array operations?
An array is a set of homogeneous elements. Every element is referred by an
index.
Arrays are used for storing the data until the application expires in the main
memory of the computer system. So that, the elements can be accessed at any
time. The operations are:
- Adding elements
- Sorting elements
- Searching elements
- Re-arranging the elements
- Performing matrix operations
- Pre-fix and post-fix operations
What is a matrix? Explain its uses with an example
A matrix is a representation of certain rows and columns, to persist homogeneous
data. It can also be called as double-dimensioned array.
Uses:
- To represent class hierarchy using Boolean square matrix
- For data encryption and decryption
- To represent traffic flow and plumbing in a network
- To implement graph theory of node representation
Define an algorithm. What are the properties of an algorithm? What are the
types of algorithms?
Algorithm: A step by step process to get the solution for a
well defined problem.
Properties of an algorithm:
- Should be written in simple English
- Should be unambiguous, precise and lucid
- Should provide the correct solutions
- Should have an end point
- The output statements should follow input, process instructions
- The initial statements should be of input statements
- Should have finite number of steps
- Every statement should be definitive
Types of algorithms:
- Simple recursive algorithms. Ex: Searching an element in a list
– Backtracking algorithms Ex: Depth-first recursive search in a tree
– Divide and conquer algorithms. Ex: Quick sort and merge sort
– Dynamic programming algorithms. Ex: Generation of Fibonacci series
– Greedy algorithms Ex: Counting currency
– Branch and bound algorithms. Ex: Travelling salesman (visiting each city once
and minimize the total distance travelled)
– Brute force algorithms. Ex: Finding the best path for a travelling salesman
– Randomized algorithms. Ex. Using a random number to choose a pivot in quick
sort).
What is an iterative algorithm?
The process of attempting for solving a problem which finds successive
approximations for solution, starting from an initial guess. The result of
repeated calculations is a sequence of approximate values for the quantities of
interest.
What is an recursive algorithm?
Recursive algorithm is a method of simplification that divides the problem into
sub-problems of the same nature. The result of one recursion is the input for
the next recursion. The repletion is in the self-similar fashion. The algorithm
calls itself with smaller input values and obtains the results by simply
performing the operations on these smaller values. Generation of factorial,
Fibonacci number series are the examples of recursive algorithms.
Explain quick sort and merge sort algorithms.
Quick sort employs the ‘divide and conquer’ concept by dividing the list of
elements into two sub elements.
The process is as follows:
1. Select an element, pivot, from the list.
2. Rearrange the elements in the list, so that all elements those are less than
the pivot are arranged before the pivot and all elements those are greater than
the pivot are arranged after the pivot. Now the pivot is in its position.
3. Sort the both sub lists – sub list of the elements which are less than the
pivot and the list of elements which are more than the pivot recursively.
Merge Sort: A comparison based sorting algorithm. The input order is preserved
in the sorted output.
Merge Sort algorithm is as follows:
1. The length of the list is 0 or 1, and then it is considered as sorted.
2. Other wise, divide the unsorted list into 2 lists each about half the size.
3. Sort each sub list recursively. Implement the step 2 until the two sub lists
are sorted.
4. As a final step, combine (merge) both the lists back into one sorted list.
What is Bubble Sort and Quick sort?
Bubble Sort: The simplest sorting algorithm. It involves the
sorting the list in a repetitive fashion. It compares two adjacent elements in
the list, and swaps them if they are not in the designated order. It continues
until there are no swaps needed. This is the signal for the list that is
sorted. It is also called as comparison sort as it uses comparisons.
Quick Sort: The best sorting algorithm which implements the
‘divide and conquer’ concept. It first divides the list into two parts by
picking an element a ’pivot’. It then arranges the elements those are smaller
than pivot into one sub list and the elements those are greater than pivot into
one sub list by keeping the pivot in its original place.
What are the difference between a stack and a Queue?
Stack – Represents the collection of elements in Last In First
Out order.
Operations includes testing null stack, finding the top element in the stack,
removal of top most element and adding elements on the top of the stack.
Queue - Represents the collection of elements in First In First
Out order.
Operations include testing null queue, finding the next element, removal of
elements and inserting the elements from the queue.
Insertion of elements is at the end of the queue
Deletion of elements is from the beginning of the queue.
Can a stack be described as a pointer? Explain.
A stack is represented as a pointer. The reason is that, it has a head pointer
which points to the top of the stack. The stack operations are performed using
the head pointer. Hence, the stack can be described as a pointer.
Explain the terms Base case, Recursive case, Binding Time, Run-Time Stack and
Tail Recursion.
Base case: A case in recursion, in which the answer is known
when the termination for a recursive condition is to unwind back.
Recursive Case: A case which returns to the answer which is
closer.
Run-time Stack: A run time stack used for saving the frame
stack of a function when every recursion or every call occurs.
Tail Recursion: It is a situation where a single recursive call
is consisted by a function, and it is the final statement to be executed. It
can be replaced by iteration.
Is it possible to insert different type of elements in a stack? How?
Different elements can be inserted into a stack. This is possible by
implementing union / structure data type. It is efficient to use union rather
than structure, as only one item’s memory is used at a time.
Explain in brief a linked list.
A linked list is a dynamic data structure. It consists of a sequence of data
elements and a reference to the next record in the sequence. Stacks, queues,
hash tables, linear equations, prefix and post fix operations. The order of
linked items is different that of arrays. The insertion or deletion operations
are constant in number.
Explain the types of linked lists.
The types of linked lists are:
Singly linked list: It has only head part and corresponding
references to the next nodes.
Doubly linked list: A linked list which both head and tail
parts, thus allowing the traversal in bi-directional fashion. Except the first
node, the head node refers to the previous node.
Circular linked list: A linked list whose last node has
reference to the first node.
How would you sort a linked list?
Step 1: Compare the current node in the unsorted list with
every element in the rest of the list. If the current element is more than any
other element go to step 2 otherwise go to step 3.
Step 2: Position the element with higher value after the
position of the current element. Compare the next element. Go to step1 if an
element exists, else stop the process.
Step 3: If the list is already in sorted order, insert the
current node at the end of the list. Compare the next element, if any and go to
step 1 or quit.
What is sequential search? What is the average number of comparisons in a
sequential search?
Sequential search: Searching an element in an array, the search
starts from the first element till the last element.
The average number of comparisons in a sequential search is (N+1)/2 where N is
the size of the array. If the element is in the 1st position, the number of
comparisons will be 1 and if the element is in the last position, the number of
comparisons will be N.
What are binary search and Fibonacci search?
Binary Search: Binary search is the process of locating an
element in a sorted list. The search starts by dividing the list into two
parts. The algorithm compares the median value. If the search element is less
than the median value, the top list only will be searched, after finding the
middle element of that list. The process continues until the element is found
or the search in the top list is completed. The same process is continued for
the bottom list, until the element is found or the search in the bottom list is
completed. If an element is found that must be the median value.
Fibonacci Search: Fibonacci search is a process of searching a
sorted array by utilizing divide and conquer algorithm. Fibonacci search
examines locations whose addresses have lower dispersion. When the search
element has non-uniform access memory storage, the Fibonacci search algorithm
reduces the average time needed for accessing a storage location.
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