# MICROSOFT PLACEMENT PAPERS

Soft Skills is all about SMARTNESS which comes through Awareness & Humbleness.

Microsoft Interview Questions

These are one of the Microsoft Interview Questions

Round 1:

1. What are your interests? ( as in academics/topics)

2. Given a string, search it in a set of strings (say among 1000s of string). What data structure would you use to store those 1000 strings and get the results fastest?
Answer:I answered hash tables but he said suggest a better
one.He said suggest a better one and then gave me one
Tree sort of DS and then asked me to compare the two.

3. Reverse a linked list?

4. Find if there is a loop in a linked List?

5. Given two arrays of numbers, find if each of the two arrays have the same set of integers ? Suggest an algo which can run faster than NlogN ?

6. Validate a Binary search tree? ( as in the left- right child follow the property )
Well i gave a the some weird eg where the struct was not a Binary tree but if passed through the test will give positive results.then he asked me to solve for that too.

Round 2:

The interviewer gets a bit serious with each stage. He will test ur work for all possible set of inputs.

Prologue: Well in my case he started with how they require not only a programmer but a designer and coder who writes perfect code.

1. Write a routine that takes input as a string such as

"aabbccdef" and o/p "a2b2c2def"
or
"a4bd2g4" for "aaaabddgggg"

write it perfectly as if it should ready to be shipped after you code it.

2. In the same Question (q1) why will u o/p "abc" for the i/p "abc" instead of "a1b1c1" ?

3. Given a NxN matrix with 0s and 1s. now whenever you encounter a 0 make the corresponding row and column elements 0.

Flip 1 to 0 and 0 remains as they are.

for example
1 0 1 1 0
0 1 1 1 0
1 1 1 1 1
1 0 1 1 1
1 1 1 1 1

results in
0 0 0 0 0
0 0 0 0 0
0 0 1 1 0
0 0 0 0 0
0 0 1 1 0

Round 3:

1. Some Questions on the projects listed on your resume?

2. Some Qs on DB Lock Manager?

3. Given 2 set of arrays of size N(sorted +ve integers ) find the median of the resultent array of size 2N.(dont even think of sorting the two arrays in a third array , though u can sort them. Try something better than order N ..order LogN )

4. Given 1000 bottles of juice, one of them contains poison and tastes bitter. Spot the spoiled bottle in minimum sips?

5. Whats the difference b/w a thread and a process? are Word and PowerPoint different processes or threads of a single process?

6. How does a spell checker routine (common to both, word and PowerPoint) used? I mean is the code copied 2 times for each of the processes in the main memory, if they are different processes or how is it used if they are threads.

7. How could you determine if a linked list contains a cycle in it, and, at what node the cycle starts?

There are a number of approaches. The approach I shared is in time N (where N is the number of nodes in your linked list). Assume that the node definition contains a boolean flag, bVisited.
struct Node
{
...
bool bVisited;
};

Then, to determine whether a node has a loop, you could first set this flag to false for all of the nodes:
// Detect cycle
// Note: pHead points to the head of the list (assume already exists)
Node *pCurrent = pHead;
while (pCurrent)
{
pCurrent->bVisited = false;
pCurrent = pCurrent->pNext;
}

A much better approach was submitted by 4Guys visitor George R., a Microsoft interviewer/employee. He recommended using the following technique, which is in time O(N) and space O(1).

Use two pointers.

// error checking and checking for NULL at end of list omitted
p1 = p2 = head;

do {
p1 = p1-gt;next;
p2 = p2-gt;next->next;
} while (p1 != p2);

p2 is moving through the list twice as fast as p1. If the list is circular, (i.e. a cycle exists) it will eventually get around to that sluggard, p1.

8. How would you reverse a doubly-linked list?

This problem isn't too hard. You just need to start at the head of the list, and iterate to the end. At each node, swap the values of pNext and pPrev. Finally, set pHead to the last node in the list.

Node * pCurrent = pHead, *pTemp;
while (pCurrent)
{ pTemp = pCurrent-gt;pNext;
pCurrent-gt;pNext = pCurrent->pPrev;
pCurrent-gt;pPrev = temp;

pHead = pCurrent;

pCurrent = temp;
}

9. Assume you have an array that contains a number of strings (perhaps char * a). Each string is a word from the dictionary. Your task, described in high-level terms, is to devise a way to determine and display all of the anagrams within the array (two words are anagrams if they contain the same characters; for example, tales and slate are anagrams.)

Begin by sorting each element in the array in alphabetical order. So, if one element of your array was slate, it would be rearranged to form aelst (use some mechanism to know that the particular instance of aelst maps to slate). At this point, you slate and tales would be identical: aelst.
Next, sort the entire array of these modified dictionary words. Now, all of the anagrams are grouped together. Finally, step through the array and display duplicate terms, mapping the sorted letters (aelst) back to the word (slate or tales).

10. Given the following prototype:
int compact(int * p, int size);

write a function that will take a sorted array, possibly with duplicates, and compact the array, returning the new length of the array. That is, if p points to an array containing: 1, 3, 7, 7, 8, 9, 9, 9, 10, when the function returns, the contents of p should be: 1, 3, 7, 8, 9, 10, with a length of 5 returned.

A single loop will accomplish this.

int compact(int * p, int size)
{
int current, insert = 1;
for (current=1; current < size; current++)
if (p[current] != p[insert-1])
{
p[insert] = p[current];
current++;
insert++;
} else
current++;
}

Microsoft Technical Interview Questions

Microsoft frequently asked interview questions, Technical interview Questions, Job interview Questions for new campus recruitment of freshers.

Microsoft interview Questions

1.What is the difference between a class and object?

2.Find the intersection of two linked lists.

3.How do you sort a linked list using the most efficient algorithm?

4. What is stored procedure? What are its advantages and disavantages?

5. Which is better trigger or stored procedure?

6.How to test a calculator?

7.Write a procedure to shuffle cards, and also mention strengths and shortcomings of your approach

8. Differnce between interfaces and abstract classes?

9.Validate a Binary search tree? ( as in the left- right child follow the property )

10.Print the binary tree in zig-zag order.

11.Sorting problem. About array

12.Whats the difference b/w a thread and a process? are Word and PowerPoint different processes or threads of a single process?

13.How does a spell checker routine (common to both, word and PowerPoint) used?

14.Design Memory Management System

15.Give all possible test cases to test the basic features of a mobile.

16. In unix there is a command called "tail". Implement that command in C.

17. Some questions about race condition (OS)

18. Questions related to semaphores.

19. Questions related to mutex. Applications of mutex. How to implement mutex in OS?

20. What is difference between data set and data reader?(.net)

21. Write a querry for accesing unique rows from emp(Ename,Age) sorted by age?

22. What is the difference between Function overloading, Function Overriding and Virtual Functions?

23. Difference between multiple and multilevel inheritence?

24. Questions about Critical region (OS).

25. Problem to find median of two shorted arrays

26. How to ensure that race condition doesn't occur. Give your view as you are OS designer.

27.. How to ensure that each process lock the critical region before they enter in it. As OS designer How will you force the process to do this?

28. Questions on IPC

29. Questions on Shared memory and Message passing mechanism.

30. Difference between system call and API call

31. How system call works? What happens when system call is invoked?

32.Remove a node from Linked list when address of same node is given

33. Different types of system calls?

34.. Some questions from microprocessor. About Interrupts

35. Types of Interrupts. What happened when interrupt is called?

36.Given a set of strings. Check if a new string is equal to any of them. Here equal means the letters are the same, like abbc=bacb

37. You are given a hard copy of a program which contains some errors. Your job is to find all types of errors from it. And discuss why is it an error. Write correct program for the same.

38. You are given a linked list and a number n. You also have a function to delete all nodes from that list which are at position which multiple of n in the list.

39.Given a string, search it in a set of strings (say among 1000s of string). What data structure would you use to store those 1000 strings and get the results fastest?

40.Reverse a linked list?

41.Find if there is a loop in a linked List?

42.Given two arrays of numbers, find if each of the two arrays have the same set of integers ? Suggest an algo which can run faster than NlogN ?

43. Questions on Java. Exception handling

44. Need of catch and finally block in Java exception handling..

45. How will you create your own exception.. Explain with example.

46. Some questions on compiler construction. What is parser? What is input to the parser and what is output of parser? Difference between top down and bottom up parser.

47.Write an algorithm to find the depth of a binary tree

48. Develop recursive program.
F(1) = 1.
F(2n) = F (n) and F(2n+1) = F(n) + F(n+1).

49.Write an algorithm to separate all zeroes and ones in an array

50.How to detect the starting point of loop in a linked list which has a loop

Microsoft  technical palcement paper with answers

1          What do ?jobs? and ?alerts? mean in Sql Server ?
Jobs: Using SQL Server Agent you can create and schedule jobs that automate routine administrative tasks. Database administrators create jobs to perform predictable administrative functions either according to a schedule or in response of events and conditions. Jobs can be simple operations containing only a single job step or can be extremely complex operations containing many job steps. SQL Server Agent is responsible for management and execution of all jobs. Agent must be running for jobs to be executed. SQL server 2k supports jobs containing operating system commands.
Alerts: database administrators define alerts to provide event and performance condition notification and to execute jobs in response to SQL server events or performance conditions. E.g. when the log is 90% full an alert can be configured to fire a job that executes a job to back up and truncate the transaction log.

2          How many groups of roles are supported in SQL Server ? Explain them
SQL Server uses roles. Two layers of access exist: access to the SQL Server and access to a database object within the server. Each can be configured separately. There are four database roles, namely: _ Public? Essentially anyone who has enough rights to connect to the database; the lowest role possible in terms of database permissions. _ db_owner? Someone who has full rights to this database, including the right to delete it altogether, create objects, and so on. _ db_data_reader? Someone who is allowed to read the data without any modifications, and who cannot create objects. _ db_datawriter? Someone who is allowed to read and write data, but who cannot create objects. These roles are contained in every database, including system databases. Every user will belong to at least one of them

3          What is T-SQL ?
Transact-SQL is a language containing the commands that are used to administer instances of SQL Server; to create and manage all objects in an instance of SQL Server; and to insert, retrieve, modify, and delete data in SQL Server tables. Transact-SQL is an extension of the language defined in the SQL standards published by the International Organization for Standardization (ISO) and the American National Standards Institute (ANSI).

A Transact-SQL statement is a set of code that performs some action on database objects or on data in a database. SQL Server supports three types of Transact-SQL statements: DDL, DCL, and DML.

A DDL statement supports the definition or declaration of database objects such as databases, tables, and views. Three DDL commands: create, alter and drop.
Data control language is used to control permissions on database objects. The DCL commands are grant and revoke.
Data manipulation language is used to select, insert, update, and delete data in the objects defined with DDL

4          What is the lock types supported in SQL Server ?
There could be thousands of concurrent users trying to read or modify the database, sometimes exactly the same data. If not for locking, your database would quickly lose its integrity. The following basic types of locks are available with SQL Server: - Shared locks: Enable users to read data but not to make modifications. - Update locks: Prevent deadlocking (discussed later in this session). - Exclusive locks: Allow no sharing; the resource under an exclusive lock is unavailable to any other transaction or process. - Schema locks: Used when table-data definition is about to change?for example, when a column is added to or removed from the table. - Bulk update locks: A special type of lock used during bulk-copy operations.

5          What is OLAP ?

Online Analytical Processing (OLAP) is by far the most complex and advanced SQL Server components. Companies are using OLAP more and more as they try to make sense of their tons of accumulated data. OLAP is used in the mysterious field called ?data
Analysis,? The standard database table represents a flat matrix; SQL Server 2000 Analysis Services use the notion of cubes. The data and corresponding objects are multidimensional, having more dimensions than our four-dimensional space-time continuum; the number of dimensions is limited only by your imagination and hardware capabilities. You must install SQL Server Analytical Services. SQL Server 2000 Analysis Services presents the data from these fact and dimension tables as multidimensional cubes that can be analyzed for trends and other information that is important for making informed business decisions.

6          Which are the two authentication modes in SQL Server 2k ?

There are two authentication modes in SQL Server 2k:  -     Windows authentication: if user is already authenticated on the windows domain as valid windows user, SQL Server 2k can be requested to trust authentication by the operating system and allow the user assess to SQL Server 2k based on these credentials. You call a connection using windows authentication as a trusted connection.-   SQL Server authentication: if the user accessing either has not been authenticated on the windows domain or wants to connect using a SQL Server 2k security account the user can request that SQL Server 2k directly authenticate the user based on submission of a username and password.

7          Which are the different services in SQL Server ? How do you manage them ?
Replication Service: SQL Server 2000 replication enables sites to maintain multiple copies of data on different computers, in order to improve overall system performance, while ensuring that all the different copies are kept synchronized.

DTS: By using DTS, you can build data warehouses and data marts in SQL Server by importing and transferring data from multiple heterogeneous sources interactively or automatically on a regularly scheduled basis.

Analysis Services: Analysis Services provides tools for analyzing the data stored in data warehouses and data marts.

Metadata services: SQL Server Meta Data Services provides a way to store and manage metadata about information systems and applications. This technology serves as a hub for data and component definitions, development and deployment models, reusable software components, and data warehousing descriptions.
Reporting services: used to generate reports from the data in the database

8          What is the lock types supported in SQL Server ?

There could be thousands of concurrent users trying to read or modify the database, sometimes exactly the same data. If not for locking, your database would quickly lose its integrity. The following basic types of locks are available with SQL Server: - Shared locks: Enable users to read data but not to make modifications. - Update locks: Prevent deadlocking (discussed later in this session). - Exclusive locks: Allow no sharing; the resource under an exclusive lock is unavailable to any other transaction or process. - Schema locks: Used when table-data definition is about to change?for example, when a column is added to or removed from the table. - Bulk update locks: A special type of lock used during bulk-copy operations.

9          How many groups of roles are supported in SQL Server ? Explain them

SQL Server uses roles. Two layers of access exist: access to the SQL Server and access to a database object within the server. Each can be configured separately. There are four database roles, namely: _ Public? Essentially anyone who has enough rights to connect to the database; the lowest role possible in terms of database permissions. _ db_owner? Someone who has full rights to this database, including the right to delete it altogether, create objects, and so on. _ db_data_reader? Someone who is allowed to read the data without any modifications, and who cannot create objects. _ db_datawriter? Someone who is allowed to read and write data, but who cannot create objects. These roles are contained in every database, including system databases. Every user will belong to at least one of them

10         Explain the Physical Structure of a Database

The SQL data is stored in the database. The data is organized into logical components that are visible to user however data is stored as files on hard disk. Each SQL server has four system databases: master, temp, msdb and model and multiple user databases. How many user databases depend from organization to organization?

The fundamental unit of data storage is page. The page size in SQL is 8KB. Every page contains a page header which is 96 bytes and stores system information such as the type of the page, amount of free space on the page, and object that owns the page.
Extents are another unit which is used to allocate space to pages and indexes. A extent is 8 continuous pages or 64 KB.

SQL server 2k has 3 types of data files: Primary data files which is the starting point of the database and points to other files, secondary data files comprise of data files other than primary data files and thirdly the log files to recover database in the event of a disaster.

Microsoft Placement Paper

1) Coldest planet:Pluto
2) INS Shivali is the first:
3) Which one of the following was NOT indegineously developed?:Prithvi/Akash/Agni
4) Full form of SARS
5) Anthrax is a :Virus/Bacteria/.../...
6) Dakshina Gangothri is:Ganga's origin/Indian camp @ antartica/.../...
7) Which of the following is a chemical weapon:Mustard Gas/Marsh Gas/.../...
8) A question based on Coding and Decoding
9) Another question similar to above
10) Question on series completion
11) Another series completion question
12) Where is Institute of Forensic Science?:Hyderabad
13)A G.K question based on chromosomes in males and females
Sample technical questions asked in test last year in CSE :
1) Banker's algorithm is used for: Deadlock Avoidance
2) A LOT of questions were based on generating strings from a given grammar.
3) A circle(dot) shown in the PCB is:Vcc/Grnd/Pin 1/Pin 14
4) Program Segment Prefix in MS-DOS 5.0 is:
5) Some IP addresses were given and the question was to select the private addess from it(?)
6) 10Base2 and 10Base5 wires refers to:
7) A question on sliding-window protocol
8) Which of the following require a driver?:disk/cache/ram/cpu
9) A LOT of mathematical questions which were asked from calculus,trigonometry...

The questions asked in ECE were mainly from Control Systems, Communications EMT and microprocessor.Make sure that u know the fundas of microprocessors useful in interview also: see if u know these questions

1. Which type of architecture 8085 has?
2. How many memory locations can be addressed by a microprocessor with 14 address lines?
3. 8085 is how many bit microprocessor?
4. Why is data bus bi-directional?
5. What is the function of accumulator?
6. What is flag, bus?
7. What are tri-state devices and why they are essential in a bus oriented system?
8. Why are program counter and stack pointer 16-bit registers?
9. What does it mean by embedded system?
10. What are the different addressing modes in 8085?
11.What is the difference between MOV and MVI?
12. What are the functions of RIM, SIM, IN?
13. What is the immediate addressing mode?
14. What are the different flags in 8085?
15. What happens during DMA transfer?
16. What do you mean by wait state? What is its need?
17. What is PSW?
18. What is ALE? Explain the functions of ALE in 8085.
19. What is a program counter? What is its use?
20. What is an interrupt?
21.Which line will be activated when an output device require attention fromCPU?

Then comes the interview questions asked in ECE interview were fundamental.Qustions asked in my interview were:

1. Which college and university are you coming from?
2. Did you appear for GATE? Why are you not interested in higher studies?
3. Did you appear for IES?
4. Did you appear for any other board interview of public sector?
5. The subjects you have learned in college can be divided into three- basic electronics, communi-cation and digital logic. Tell me any five subjects you like.
(I told radar and navigational aids, electronic warfare, satellite communication, biomedical instrumentation, fuzzy electronics and basic digital electronics as my subjects)

Board member1 (QUESTION LEVEL- MODERATE)
1. Write the truth table for full adder and implement it in NAND gate only.
2. What's the difference between looping 0s and 1s in K map?
3. Difference between microprocessor and micro controller
4. Microprocessors you are familiar with
5. How will you send and receive data to a micro-processor? (One method is I/O mapped I/O which is the other one?)
6. Radar range equation?
7. Does the radar range depend upon the frequency of the signal transmitted?
8. What is Doppler shift? What is its importance?

BOARD MEMBER -2 QUESTION LEVEL- TOUGH)
1. I will make two fuzzy statements. Pencil is long. Table is long. What is the term long signify?
2. What is a membership function?
3. What are the design criteria for very low frequency amplifier?
4. Can you measure distance with the help of CW radar? If so how?
5. How will you design a stable oscillator? (Not with crystal oscillator because temperature affects it)
6. You have designed an amplifier. After few days it is found that its gain have changed. What might be the reason?

BOARD MEMBER-3 (QUESTION LEVEL- MODERATE)
1. A plane is moving in a circular path around the transmitter of the radar. Will there be Doppler shift detected in the radar?
2. State Keplers laws
3. Why there is more geo synchronous satellite?
4. The angular difference between two satellites is 2 degree. What is the maximum number of satellites needed to cover the whole earth?
5. What is the minimum number of satellites needed to cover the whole earth?

BOARD MEMBER-4 QUESTION LEVEL- MODERATE)
1. Which is the law of conservation involved in the second of Keplers?
2. Why do you explain elliptical orbit while stating Kepler's law? Why not circular orbit?
3. What are the advantages of optical communication?
4. What are the invasive and non-invasive methods of instrumentation?

For CS guys they started with this question: What is a key board? Where u will connec? What will happen if you press the keys?..
For maths guys they asked some questions on series.. I don't know muchSome guys were selected just by describing the final year project.

1. How can you design a phase detector using a XOR gate?
2. Questions abt differentiator and integrator. What will happen if we increase/decrease the values of R/C?
3. how will a low/high pass filters behave to different signals
–ramp, pulse etc
4. questions on flip flops
5. Johnson counter
6. Questions on microprocessors- what is SIM?
7. Abt your project. What will happen when this/that happens to your project?
8. Radar, antenna and satellite communication.
9. Which is the first/latest communication satellite?
10. What is apogee /perigee?

Algorithms and Programming

1. Given a rectangular (cuboidal for the puritans) cake with a rectangular piece removed (any size or orientation), how would you cut the remainder of the cake into two equal halves with one straight cut of a knife ?

2. You're given an array containing both positive and negative integers and required to find the sub-array with the largest sum (O(N) a la KBL). Write a routine in C for the above.

3. Given an array of size N in which every number is between 1 and N, determine if there are any duplicates in it. You are allowed to destroy the array if you like. [ I ended up giving about 4 or 5 different solutions for this, each supposedly better than the others ].

4. Write a routine to draw a circle (x ** 2 + y ** 2 = r ** 2) without making use of any floating point computations at all. [ This one had me stuck for quite some time and I first gave a solution that did have floating point computations ].

5. Given only putchar (no sprintf, itoa, etc.) write a routine putlong that prints out an unsigned long in decimal. [ I gave the obvious solution of taking % 10 and / 10, which gives us the decimal value in reverse order. This requires an array since we need to print it out in the correct order. The interviewer wasn't too pleased and asked me to give a solution which didn't need the array ].

6. Give a one-line C expression to test whether a number is a power of 2. [No loops allowed - it's a simple test.]

7. Given an array of characters which form a sentence of words, give an efficient algorithm to reverse the order of the words (not characters) in it.

8. How many points are there on the globe where by walking one mile south, one mile east and one mile north you reach the place where you started.

9. Give a very good method to count the number of ones in a "n" (e.g. 32) bit number.
ANS. Given below are simple solutions, find a solution that does it in log (n) steps.

Iterative
function iterativecount (unsigned int n)
begin
int count=0;
while (n)
begin
count += n & 0x1 ;
n >>= 1;
end
return count;
end
Sparse Count
function sparsecount (unsigned int n)
begin
int count=0;
while (n)
begin
count++;
n &= (n-1);
end
return count ;
end

10. What are the different ways to implement a condition where the value of x can be either a 0 or a 1. Apparently the if then else solution has a jump when written out in assembly. if (x == 0) y=a else y=b There is a logical, arithmetic and a data structure solution to the above problem.

11. Reverse a linked list.

12. Insert in a sorted list

13. In a X's and 0's game (i.e. TIC TAC TOE) if you write a program for this give a fast way to generate the moves by the computer. I mean this should be the fastest way possible.
The answer is that you need to store all possible configurations of the board and the move that is associated with that. Then it boils down to just accessing the right element and getting the corresponding move for it. Do some analysis and do some more optimization in storage since otherwise it becomes infeasible to get the required storage in a DOS machine.

14. I was given two lines of assembly code which found the absolute value of a number stored in two's complement form. I had to recognize what the code was doing. Pretty simple if you know some assembly and some fundaes on number representation.

15. Give a fast way to multiply a number by 7.

16. How would go about finding out where to find a book in a library. (You don't know how exactly the books are organized beforehand).

17. Linked list manipulation.

18. Tradeoff between time spent in testing a product and getting into the market first.

19. What to test for given that there isn't enough time to test everything you want to.

20. First some definitions for this problem: a) An ASCII character is one byte long and the most significant bit in the byte is always '0'. b) A Kanji character is two bytes long. The only characteristic of a Kanji character is that in its first byte the most significant bit is '1'.
Now you are given an array of a characters (both ASCII and Kanji) and, an index into the array. The index points to the start of some character. Now you need to write a function to do a backspace (i.e. delete the character before the given index).

21. Delete an element from a doubly linked list.

22. Write a function to find the depth of a binary tree.

23. Given two strings S1 and S2. Delete from S2 all those characters which occur in S1 also and finally create a clean S2 with the relevant characters deleted.

24. Assuming that locks are the only reason due to which deadlocks can occur in a system. What would be a foolproof method of avoiding deadlocks in the system.

25. Reverse a linked list.
Ans: Possible answers -
iterative loop
curr->next = prev;
prev = curr;
curr = next;
next = curr->next
endloop
recursive reverse(ptr)
if (ptr->next == NULL)
return ptr;
temp = reverse(ptr->next);
temp->next = ptr;
return ptr;
end

26. Write a small lexical analyzer - interviewer gave tokens. expressions like "a*b" etc.

27. Besides communication cost, what is the other source of inefficiency in RPC? (answer : context switches, excessive buffer copying). How can you optimize the communication? (ans : communicate through shared memory on same machine, bypassing the kernel _ A Univ. of Wash. thesis)

28. Write a routine that prints out a 2-D array in spiral order!

29. How is the readers-writers problem solved? - using semaphores/ada .. etc.

30. Ways of optimizing symbol table storage in compilers.

31. A walk-through through the symbol table functions, lookup() implementation etc. - The interviewer was on the Microsoft C team.

32. A version of the "There are three persons X Y Z, one of which always lies".. etc..

33. There are 3 ants at 3 corners of a triangle, they randomly start moving towards another corner.. what is the probability that they don't collide.

34. Write an efficient algorithm and C code to shuffle a pack of cards.. this one was a feedback process until we came up with one with no extra storage.

35. The if (x == 0) y = 0 etc..

36. Some more bitwise optimization at assembly level

37. Some general questions on Lex, Yacc etc.

38. Given an array t which contains numbers between 1..99. Return the duplicated value. Try both O(n) and O(n-square).

39. Given an array of characters. How would you reverse it. ? How would you reverse it without using indexing in the array.

40. Given a sequence of characters. How will you convert the lower case characters to upper case characters. ( Try using bit vector - solutions given in the C lib -typec.h)

41. Fundamentals of RPC.

42. Given a linked list which is sorted. How will u insert in sorted way.

43. Given a linked list How will you reverse it.

44. Give a good data structure for having n queues ( n not fixed) in a finite memory segment. You can have some data-structure separate for each queue. Try to use at least 90% of the memory space.

45. Do a breadth first traversal of a tree.

46. Write code for reversing a linked list.

47. Write, efficient code for extracting unique elements from a sorted list of array. e.g. (1, 1, 3, 3, 3, 5, 5, 5, 9, 9, 9, 9) -> (1, 3, 5, 9).

48. Given an array of integers, find the contiguous sub-array with the largest sum.

ANS. Can be done in O(n) time and O(1) extra space. Scan array from 1 to n. Remember the best sub-array seen so far and the best sub-array ending in i.

49. Given an array of length N containing integers between 1 and N, determine if it contains any duplicates.
ANS. [Is there an O(n) time solution that uses only O(1) extra space and does not destroy the original array?]

50. Sort an array of size n containing integers between 1 and K, given a temporary scratch integer array of size K.
ANS. Compute cumulative counts of integers in the auxiliary array. Now scan the original array, rotating cycles! [Can someone word this more nicely?]

* 51. An array of size k contains integers between 1 and n. You are given an additional scratch array of size n. Compress the original array by removing duplicates in it. What if k << n?
ANS. Can be done in O(k) time i.e. without initializing the auxiliary array!

52. An array of integers. The sum of the array is known not to overflow an integer. Compute the sum. What if we know that integers are in 2's complement form?
ANS. If numbers are in 2's complement, an ordinary looking loop like for(i=total=0;i< n;total+=array[i++]); will do. No need to check for overflows!

53. An array of characters. Reverse the order of words in it.
ANS. Write a routine to reverse a character array. Now call it for the given array and for each word in it.
* 54. An array of integers of size n. Generate a random permutation of the array, given a function rand_n() that returns an integer between 1 and n, both inclusive, with equal probability. What is the expected time of your algorithm?

ANS. "Expected time" should ring a bell. To compute a random permutation, use the standard algorithm of scanning array from n downto 1, swapping i-th element with a uniformly random element <= i-th. To compute a uniformly random integer between 1 and k (k < n), call rand_n() repeatedly until it returns a value in the desired range.

55. An array of pointers to (very long) strings. Find pointers to the (lexicographically) smallest and largest strings.
ANS. Scan array in pairs. Remember largest-so-far and smallest-so-far. Compare the larger of the two strings in the current pair with largest-so-far to update it. And the smaller of the current pair with the smallest-so-far to update it. For a total of <= 3n/2 strcmp() calls. That's also the lower bound.

56. Write a program to remove duplicates from a sorted array.
ANS. int remove_duplicates(int * p, int size)
{
int current, insert = 1;
for (current=1; current < size; current++)
if (p[current] != p[insert-1])
{
p[insert] = p[current];
current++;
insert++;
} else
current++;
return insert;
}

57. C++ ( what is virtual function ? what happens if an error occurs in constructor or destructor. Discussion on error handling, templates, unique features of C++. What is different in C++, ( compare with unix).

58. Given a list of numbers ( fixed list) Now given any other list, how can you efficiently find out if there is any element in the second list that is an element of the first list (fixed list).

59. Given 3 lines of assembly code : find it is doing. IT was to find absolute value.

60. If you are on a boat and you throw out a suitcase, Will the level of water increase.

61. Print an integer using only putchar. Try doing it without using extra storage.

62. Write C code for (a) deleting an element from a linked list (b) traversing a linked list

63. What are various problems unique to distributed databases

64. Declare a void pointer ANS. void *ptr;

65. Make the pointer aligned to a 4 byte boundary in a efficient manner ANS. Assign the pointer to a long number and the number with 11...1100 add 4 to the number

66. What is a far pointer (in DOS)

67. What is a balanced tree

68. Given a linked list with the following property node2 is left child of node1, if node2 < node1 else, it is the right child.
O P
|
|
O A
|
|
O B
|
|
O C
How do you convert the above linked list to the form without disturbing the property. Write C code for that.
O P
|
|
O B
/ \
/   \
/     \
O ?     O ?
determine where do A and C go

69. Describe the file system layout in the UNIX OS
ANS. describe boot block, super block, inodes and data layout

70. In UNIX, are the files allocated contiguous blocks of data
ANS. no, they might be fragmented
How is the fragmented data kept track of
ANS. Describe the direct blocks and indirect blocks in UNIX file system

71. Write an efficient C code for 'tr' program. 'tr' has two command line arguments. They both are strings of same length. tr reads an input file, replaces each character in the first string with the corresponding character in the second string. eg. 'tr abc xyz' replaces all 'a's by 'x's, 'b's by 'y's and so on. ANS.
a) have an array of length 26.
put 'x' in array element corr to 'a'
put 'y' in array element corr to 'b'
put 'z' in array element corr to 'c'
put 'd' in array element corr to 'd'
put 'e' in array element corr to 'e'
and so on.
the code
while (!eof)
{
c = getc();
putc(array[c - 'a']);
}

72. what is disk interleaving

73. why is disk interleaving adopted

74. given a new disk, how do you determine which interleaving is the best a) give 1000 read operations with each kind of interleaving determine the best interleaving from the statistics

75. draw the graph with performance on one axis and 'n' on another, where 'n' in the 'n' in n-way disk interleaving. (a tricky question, should be answered carefully)

76. I was a c++ code and was asked to find out the bug in that. The bug was that he declared an object locally in a function and tried to return the pointer to that object. Since the object is local to the function, it no more exists after returning from the function. The pointer, therefore, is invalid outside
.
77. A real life problem - A square picture is cut into 16 squares and they are shuffled. Write a program to rearrange the 16 squares to get the original big square.

78.
int *a;
char *c;
*(a) = 20;
*c = *a;
printf("%c",*c);
what is the output?

79. Write a program to find whether a given m/c is big-endian or little-endian!

80. What is a volatile variable?

81. What is the scope of a static function in C ?

82. What is the difference between "malloc" and "calloc"?

83. struct n { int data; struct n* next}node;
node *c,*t;
c->data = 10;
t->next = null;
*c = *t;
what is the effect of the last statement?

84. If you're familiar with the ? operator x ? y : z

you want to implement that in a function: int cond(int x, int y, int z); using only ~, !, ^, &, +, |, <<, >> no if statements, or loops or anything else, just those operators, and the function should correctly return y or z based on the value of x. You may use constants, but only 8 bit constants. You can cast all you want. You're not supposed to use extra variables, but in the end, it won't really matter, using vars just makes things cleaner. You should be able to reduce your solution to a single line in the end though that requires no extra vars.

85. You have an abstract computer, so just forget everything you know about computers, this one only does what I'm about to tell you it does. You can use as many variables as you need, there are no negative numbers, all numbers are integers. You do not know the size of the integers, they could be infinitely large, so you can't count on truncating at any point. There are NO comparisons allowed, no if statements or anything like that. There are only four operations you can do on a variable.
1) You can set a variable to 0.
2) You can set a variable = another variable.
3) You can increment a variable (only by 1), and it's a post increment.
4) You can loop. So, if you were to say loop(v1) and v1 = 10, your loop would execute 10 times, but the value in v1 wouldn't change so the first line in the loop can change value of v1 without changing the number of times you loop.

You need to do 3 things.
1) Write a function that decrements by 1.
2) Write a function that subtracts one variable from another.
3) Write a function that divides one variable by another.
4) See if you can implement all 3 using at most 4 variables. Meaning, you're not making function calls now, you're making macros. And at most you can have 4 variables. The restriction really only applies to divide, the other 2 are easy to do with 4 vars or less. Division on the other hand is dependent on the other 2 functions, so, if subtract requires 3 variables, then divide only has 1 variable left unchanged after a call to subtract. Basically, just make your function calls to decrement and subtract so you pass your vars in by reference, and you can't declare any new variables in a function, what you pass in is all it gets.
Linked lists

* 86. Under what circumstances can one delete an element from a singly linked list in constant time?
ANS. If the list is circular and there are no references to the nodes in the list from anywhere else! Just copy the contents of the next node and delete the next node. If the list is not circular, we can delete any but the last node using this idea. In that case, mark the last node as dummy!

* 87. Given a singly linked list, determine whether it contains a loop or not.
ANS. (a) Start reversing the list. If you reach the head, gotcha! there is a loop!
But this changes the list. So, reverse the list again.
(b) Maintain two pointers, initially pointing to the head. Advance one of them one node at a time. And the other one, two nodes at a time. If the latter overtakes the former at any time, there is a loop!
p1 = p2 = head;
do {
p1 = p1->next;
p2 = p2->next->next;
} while (p1 != p2);

88. Given a singly linked list, print out its contents in reverse order. Can you do it without using any extra space?
ANS. Start reversing the list. Do this again, printing the contents.

89. Given a binary tree with nodes, print out the values in pre-order/in-order/post-order without using any extra space.

90. Reverse a singly linked list recursively. The function prototype is node * reverse (node *) ;
ANS.
node * reverse (node * n)
{
node * m ;
if (! (n && n -> next))
return n ;
m = reverse (n -> next) ;
n -> next -> next = n ;
n -> next = NULL ;
return m ;
}
91. Given a singly linked list, find the middle of the list.
HINT. Use the single and double pointer jumping. Maintain two pointers, initially pointing to the head. Advance one of them one node at a time. And the other one, two nodes at a time. When the double reaches the end, the single is in the middle. This is not asymptotically faster but seems to take less steps than going through the list twice.

Bit-manipulation
92. Reverse the bits of an unsigned integer.
ANS.
#define reverse(x)                              \
(x=x>>16|(0x0000ffff&x)<<16,            \
x=(0xff00ff00&x)>>8|(0x00ff00ff&x)<<8, \
x=(0xf0f0f0f0&x)>>4|(0x0f0f0f0f&x)<<4, \
x=(0xcccccccc&x)>>2|(0x33333333&x)<<2, \
x=(0xaaaaaaaa&x)>>1|(0x55555555&x)<<1)
* 93. Compute the number of ones in an unsigned integer.
ANS.
#define count_ones(x)                        \
(x=(0xaaaaaaaa&x)>>1+(0x55555555&x), \
x=(0xcccccccc&x)>>2+(0x33333333&x), \
x=(0xf0f0f0f0&x)>>4+(0x0f0f0f0f&x), \
x=(0xff00ff00&x)>>8+(0x00ff00ff&x), \
x=x>>16+(0x0000ffff&x))
94. Compute the discrete log of an unsigned integer.
ANS.
#define discrete_log(h) \
(h=(h>>1)|(h>>2), \
h|=(h>>2), \
h|=(h>>4), \
h|=(h>>8), \
h|=(h>>16), \
h=(0xaaaaaaaa&h)>>1+(0x55555555&h), \
h=(0xcccccccc&h)>>2+(0x33333333&h), \
h=(0xf0f0f0f0&h)>>4+(0x0f0f0f0f&h), \
h=(0xff00ff00&h)>>8+(0x00ff00ff&h), \
h=(h>>16)+(0x0000ffff&h))
If I understand it right, log2(2) =1, log2(3)=1, log2(4)=2..... But this macro does not work out log2(0) which does not exist! How do you think it should be handled?
* 95. How do we test most simply if an unsigned integer is a power of two?
ANS. #define power_of_two(x) \ ((x)&&(~(x&(x-1))))
96. Set the highest significant bit of an unsigned integer to zero.
ANS. (from Denis Zabavchik) Set the highest significant bit of an unsigned integer to zero
#define zero_most_significant(h) \
(h&=(h>>1)|(h>>2), \
h|=(h>>2), \
h|=(h>>4), \
h|=(h>>8), \
h|=(h>>16))
97. Let f(k) = y where k is the y-th number in the increasing sequence of non-negative integers with the same number of ones in its binary representation as y, e.g. f(0) = 1, f(1) = 1, f(2) = 2, f(3) = 1, f(4) = 3, f(5) = 2, f(6) = 3 and so on. Given k >= 0, compute f(k).

Others
98. A character set has 1 and 2 byte characters. One byte characters have 0 as the first bit. You just keep accumulating the characters in a buffer. Suppose at some point the user types a backspace, how can you remove the character efficiently. (Note: You cant store the last character typed because the user can type in arbitrarily many backspaces)
99. What is the simples way to check if the sum of two unsigned integers has resulted in an overflow.
100. How do you represent an n-ary tree? Write a program to print the nodes of such a tree in breadth first order.
101. Write the 'tr' program of UNIX. Invoked as
tr -str1 -str2. It reads stdin and prints it out to stdout, replacing every occurance of str1[i] with str2[i].
e.g. tr -abc -xyz
to be and not to be <- input
to ye xnd not to ye <- output

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