These are some of the possibilities that I should be expecting:
premonition
predilection
prediction
etc.

So, a possible expression can be:

^(pre)+([a-z]*|[A-Z]*|\\s)*(ion)+\$

Any word that beings with the atom “pre”, in which the atom “pre” Must occur at least one time and can occur more than one time after the beginning, and there can be 0 or many characters in the middle, starting from a-z OR A-Z OR space characters with a quantifier *, which indicates that the characters can occur 0 or more times, with an external quantifier that ensures that the letter case is ignored during the match, and it only matches the patterns that end with the atom, “ion”, which is specified by the concluding $

Example 2:

^?[0-9]+(ord)+\$?

Says that the atom ‘ord’ has to be preceded at least once by a number. The + quantifier after [0-9] signifies that the numbers can be repeated any number of times. Also the ^? signifies that the numbers need not start from the beginning of the pattern in question. Also what the “\$?” means is that the pattern need not essentially end with the atom “ord”

vinay@darkbox:~$ sudo apt-get install blah-app

………………

After printing some packages that need to be updated

…………..

………

[b]Media change: please insert the disc labeled
‘xxxxxxxxxxxx_xxxxxxxxxx_ -xxxxxxxxx(xxxxxxxx)’
in the drive ‘/cdrom/’ and press enter
<enter>
Media change: please insert the disc labeled
‘xxxxxxxxxxxx_xxxxxxxxxx_ -xxxxxxxxx(xxxxxxxx)’
in the drive ‘/cdrom/’ and press enter

** The xxxxxxxxxxxx_xxxxxxxxxx_ -xxxxxxxxx(xxxxxxxx) can be anything depending on your distro.

A solution for this is to comment out the source list that points to the CD-ROM on the apt sources. So I did this:

vi /etc/apt/sources.list and comment the line that reads something similar to this:

deb cdrom:[ xxxxxxxxxxxx_xxxxxxxxxx_ -xxxxxxxxx(xxxxxxxx) ]/ hoary main restricted

This will restrict the apt tool from looking back to CD-ROM for the sources and quit. There may be some other approaches for this problem. It would be helpful if anyone who reads this thread discuss those approaches here.

Good Luck!

A pirate arranges his cannon balls as show in the following way:

In the first arrangement, there is only one cannon ball. To support it, he inserts 3 cannon balls under it. And to support those 3, 6 would be placed under them and so on. Now if you count the balls in each case it would follow a series like 1 , 4 , 10 …. Write a logic for generating this.

This is interesting puzzle. As we can see, the cannon balls have some embedded pattern in them:

1

1 + (1+2)

1+ (1+2) + (1+2+3)

and so on.

A little math knowledge would help here. If you are aware of the formula for first N natural numbers, it is

N* (N+1) / 2. This can be extended to this puzzle easily to calculate the series. Here is how it can be applied

1*(1+1)/2

1*(1+1)/2 + 2 * (2+1)/2

1*(1+1)/2 + 2 * (2+1)/2 + 3*(3+1)/2

and so on.

As can be seen, we could apply a Sigma operator to condense this formula a little bit:

∑ n * (n+1)/2

for n = 1 to n

Now that we have a cute little Math counter in our hand, we can code it fast. Here is what I did:

public class TetrahedralNumbers {

public static void main(String[] args){

int cannon = 0;
for(int i = 1; i < 14; i++)
{
cannon += (i * (i+1))/2;
System.out.println(cannon);
}
}

}

If you are unaware of the Math part and want to go solving this, there is a slightly inefficient approach that still solves the puzzle:

public class TetrahedralNumbers {

public static void main(String[] args)
{
for (int i = 1; i < 10; i++)
{
int count = 0;

for(int j = 1; j <= i; j++)
{
for(int k = 1; k <= j; k++)
{
count += k;
}
}
System.out.println(count);
}
}

}

http://virtualbox.wordpress.com/images/

This place has a gorgeous collection of images. You can pick one from them too. But the latest distribution of CentOS comes with no GUI.So I wanted to have Gnome on my new CentOS baby. Luckily it had wget, yum for rescue. Here is what I did after booting up the image and logging in as root (don’t follow this before you read entire article):

yum groupinstall “X Window System” “GNOME Desktop Environment”

After downloading a bunch of packages, it complained about the absense of  a “libgaim.so.0″ package that is needed by “nautilus-sendto” package. You would see something like this:

0002483: nautilus-sendto requires a non-existent libgaim.so.0

Fortunately, it’s a known bug: http://bugs.centos.org/view.php?id=2483

The solution is to get an rpm package and install it with nodeps option. So here is what you need to do:

wget http://mirror.centos.org/centos/5/os/i386/CentOS/nautilus-sendto-0.7-5.fc6.i386.rpm

After downloading the package, install it as follows:

rpm -Uvh –nodeps nautilus-sendto-0.7-5.fc6.i386.rpm

Once this is done, type in this:

yum groupinstall “X Window System” “GNOME Desktop Environment”

That’s it. Your headless centOS is equipped with Gnome!

Here is the scenario… I have a text file in this format:

Gasoline Mexico $2.5

Gasoline USA $4.5

Gasoline Afghanistan $85

Beer Mexico $1.25

Beer USA $2.85

Beer Afghanistan $0.0

Now I want to query for ‘gasoline’ and get a map of all ‘country —> price’ listings. Similarly, I want to ask for beer and get a list of ‘country —> price’. This can be easily done by building a hashmap of hashmaps. As a visual guide, this is how the Datastructure will look like, after we’re done designing it:

My Approach:

Hashmap<String,Properties> gasBeerMap = new HashMap<String,Properties>();

//read the text file, get the inputstream

while(there are more lines in the textfile)

{

String[] tokens = tokenize the line;

Properties tmp = (Properties) gasBeerMap.get(tokens[0]);

if(tmp == null)

{

tmp = new Properties();
_gasBeerMap.put(tokens[0],tmp);

}

tmp.setProperty(tokens[1],tokens[2]);

}

This will check if the map for a specific entry is null. If it is, then it will insert a new map to that specific entry as it’s mapped value. As it can be observed, for the next iterations, the map will only get updated. This is one approach to the problem. Let me know if you have some cool approaches to this problem

]]> http://vinaychilakamarri.wordpress.com/2008/07/30/creating-a-hashmap-of-hashmaps-in-java/feed/ 0 vinaychilakamarri http://vinaychilakamarri.wordpress.com/2008/07/29/exporting-your-java-project-to-a-jar-file-in-two-clicks-using-fat-jar-plugin/ http://vinaychilakamarri.wordpress.com/2008/07/29/exporting-your-java-project-to-a-jar-file-in-two-clicks-using-fat-jar-plugin/#comments Tue, 29 Jul 2008 06:30:38 +0000 vinaychilakamarri http://vinaychilakamarri.wordpress.com/?p=28 ]]> Sick and tired of writing manifest files and arranging jar files and class files, I searched to see if I can find some click-click-click eclipse feature that will do this job for me. And the answer came in after a brief googling: The fat-jar plugin. Installing this plugin’s zip is easy. Extract the zip to some place and copy the folder under ‘plugins’ to the actual eclipse plugins directory. Restart the eclipse and you should see a ‘Build Fat jar’ with a green cross when you right click on your project. Here is the tutorial on how to build the jar file after you are done with the plaugin installation:

http://fjep.sourceforge.net/fjeptutorial.html

Happy jar building!

………………..
$file = shift;
open FILE, $file or die “Couldn’t open the file $file”; #note this
…………………

The second step can also be written in this way:
open FILE, $file || die “Couldn’t open the file $file”; #note this

But when the execution of this program happens, you will never see the message in ‘die’, if you use a || instead of ‘or’. Reason for this is that the || operator has a precedence level higher than that of ‘or’ and since
the ‘open FILE, $file’ returns a value after an attempt to execute, the || is always true and die is never reached.

The actual reason as Martin, one of the commentators  puts it,

The actual reason is that the operator precedence for the double pipe is higher than the comma, so perl is resolving the double pipe first, which chooses the first true result of its two parameters, in this case $file and the die statement. As long as $file is a nonempty string it counts as true and always gets returned by the double pipe.

So it is always advisable to use ‘or’ instead of ||. If you want to use ‘||’, you can do it by using the
pen file with parathesis which ensures the precedence of the operators.

open (FILE, $file) || die “Couldn’t open the file $file”;

sub printFileContent {

foreach(@_){

printInsideThings ($_);
}
}

sub printInsideThings {
open FILE,$_;
while($line = <FILE>){
print $line;
}
}

printFileContent (“C:\\Data\\virtual-hosting-howto.html”,”C:\\Data\\virtual-boasting-howto.html”);

As I pass a list of files, the ‘@_’ of my first sub is already initialized with the list of strings that I passed.
So I used ‘foreach’ and passed the “$_” to another subroutine. The ‘$_’ will be initialized to the list item for
each iteration over the list. The other sub takes the string, and using a ‘$_’, which is initialized with the passed value by default, it opens the file and initializes a global variable ‘FILE’ and prints the content line by line in the while loop. The ‘< >’ opens the file and reads it line by line for you (uber cool tool eh?). Other ways we can do the later subroutine:

sub printInsideThings {
open FILE,shift;
while(<FILE>){
print ;
}
}

Look at the while loop there. Perl uses the ‘$_’ so implicitly that you don’t even have to specify it. That loop initializes the ‘$_’ for every iteration and assigns it the line it reads from the file. The “print;” is equivalent to “print $_;” Again, the ‘shift’ in that file opener takes out the first of the ‘@_’ and passes it for parsing stuff

This one prints the contents of a single file that is passed:

sub openFu{
open FILE, shift;
while(<FILE>){
print;
}
}

openFu “c:\\data\\virtual-hosting-howto.html”;

@arr = qw(i can be a bad guy);

$var = @arr;

print “$var”;

This will print 6. In the same way we can also use an inbuilt function for this. The function is called ‘scalar’

$var = scalar(@arr); assigns the size of the array. In the same way we can also initialize a variable to a list. But the variable will get initialized to the last variable of that list. For example:

$var = (1,2,3,4); will initialize $var to 4.

Here is the code I wrote:

# !/usr/bin/perl
@array = (‘A’ .. ‘Z’);
$in = <>;
chomp($in);
if($in < 0)
{
print “Can’t proceed”;
}
else{
for($i = 0 ; $i < $in ; $i++)
{
@tmp = (”);
for($k = scalar(@array); $k > $i; $k–)
{
print ” “;
}
for($j = 0 ; $j < $i; $j++)
{
push(@tmp,@array[$j]);
print “@array[$j]“;
}
pop(@tmp);
@revtmp = reverse(@tmp);
foreach(@revtmp)
{ print “$_” ;}
print “\n”;
}
}

This is a rough attempt at the problem. It can be:
1. Checked for input validity

2. Enhanced with what ever you want to ice on top of it.

Have fun!