MICROSOFT PLACEMENT PAPER (TECHNICALC, OS)
PAPER: MICROSOFT PLACEMENT PAPER (TECHNICALC, OS)
1. 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!
2. 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!
3. 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.
4. 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 ith element with a uniformly random element <= ith. 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.
5. An array of pointers to (very long) strings. Find pointers to the (lexicographically) smallest and largest strings.
ANS. Scan array in pairs. Remember largestsofar and smallestsofar. Compare the larger of the two strings in the current pair with largestsofar to update it. And the smaller of the current pair with the smallestsofar to update it. For a total of <= 3n/2 strcmp() calls. That's also the lower bound.
6. 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[insert1])
{
p[insert] = p[current];
current++;
insert++;
} else
current++;
return insert;
}
7. 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).
8. 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).
9. Given 3 lines of assembly code : find it is doing. IT was to find absolute value.
10. If you are on a boat and you throw out a suitcase, Will the level of water increase.
11. Print an integer using only putchar. Try doing it without using extra storage.
12. Write C code for (a) deleting an element from a linked list (b) traversing a linked list
13. What are various problems unique to distributed databases
14. Declare a void pointer ANS. void *ptr;
15. 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
16. What is a far pointer (in DOS)
17. What is a balanced tree
18. 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
19. Describe the file system layout in the UNIX OS
ANS. describe boot block, super block, inodes and data layout
20. In UNIX, are the files allocated contiguous blocks of data
ANS. no, they might be fragmented
21.How is the fragmented data kept track of Describe the direct blocks and indirect blocks in UNIX file system
22. 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']);
}
23. what is disk interleaving
24. why is disk interleaving adopted
25. 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
26. draw the graph with performance on one axis and 'n' on another, where 'n' in the 'n' in nway disk interleaving. (a tricky question, should be answered carefully
Companies List:
3i Infotech  AAI  ABACUS  ABB  Accel Frontline  Accenture  Aditi  Adobe  ADP  Agreeya  Akamai  Alcatel Lucent  Allfon  Alumnus  Amazon  Amdocs  AMI  Andhra Bank  AppLabs  Apps Associates  Aricent  Ashok Leyland  Aspire  Atos Origin  Axes  Bajaj  Bank of Maharashtra  BEL  BEML  BHEL  BirlaSoft  Blue Dart  Blue Star  BOB  BPCL  BPL  Brakes  BSNL  CDOT  Cadence  Calsoft  Canara Bank  Canarys  Capgemini  Caritor  Caterpillar  CDAC  CGI  Changepond  Ciena  Cisco  Citicorp  CMC  Consagous  Convergys  CORDYS  Crompton  CSC  CTS  Cummins  Dell  Deloitte  DelphiTVS  DeShaw  Deutsche  Dotcom  DRDO  EDS  EIL  ELGI  ELICO  ERICSSON  Essar  Fidelity  Flextronics  Freescale  FXLabs  GAIL  GE  Genpact  Geodesic  Geometric  Globaledge  GlobalLogic  Godrej  Google  Grapecity  HAL  HCL  Hexaware  Honeywell  HP  HPCL  HSBC  Huawei  Hughes  IBM  IBS  ICICI  iGate  Impetus  iNautix  Indian Airforce  Indian Airlines  Infosys  Infotech  Intec  Integra  Intergraph  IOCL  iSOFT  ISRO  Ittiam  JSW  Keane  Kenexa  L & T  L & T Infotech  LG Soft  Lifetree  LionBridge  Mahindra Satyam  Mastek  Maveric  McAfee  MECON  Microsoft  MindTree  Miraclesoft  Mistral  Motorola  Mphasis  MTNL  NIC  Nokia Siemens  Novell  NTPC  Nucleus  ORACLE  Patni  Perot  Polaris  Ramco  Robert Bosch  Samsung  SAP  Sapient  Sasken  SBI  Sierra Atlantic  Sonata  Sony India  Sutherland  Syntel  TCS  Tech Mahindra  VeriFone  Virtusa  Wipro  Zensar.