Programming Challenges

Multiplication by 2 is most often optimized into var << 1.

The lucky thing with binary multiplicaiton is EVERYTHING is a multiple of 2, so shifts are all you need. After all the shifts you still need to add the individual products just as we do with decimal math.

I found this animated picture that illustrates multiplication very well.

http://www.is.wayne.edu/drbowen/casw01/AnimMult.gif

Quote:

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Originally posted by tecknophreak
Sure did. :D

how's the "for loop in range(x)" work? and how do you know a loop(while/for) is done? cause in C/C++, etc, you have the { } to tell ya.

P.S. you can do lose two lines from your code. ;)

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In python range(x) gives you a list from 0 to x.

In Python, your loop / condition ends at the next unindented line. Thus you always have pretty looking code ;)

Quote:

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Originally posted by Trogdor
I'm doing a project for my compy sci class. I'll have three years to work on it. I am going to do it in PHP (so I can make it on my linux box and run it on my teacher's winblows 98 . . . also for the MySQL integration), and I need a good idea for my project. There are seven requirements, that I must show mastery in my program. Almost all of them I could do in my sleep, but I need a good idea.
1. Arrays || Records || Objects
2. Selection Constructs (branching)
3. Iteration Constructs (looping)
4. subprograms (built-in && user defined)
5. parameter passing (hah!)
6. Sorting || Searching Techniques
7. File Access

It looks like a job for MySQL. But what should I make? Any ideas?

Thanks,
TROGDOR!!!

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I thought of something today that I'm not sure has ever been done. What about a website where people can go and store a list of favorites....like the favorites folder, but accessible anywhere. Users would log into their account to access and edit their list. You would have to allow new accounts to be created, possibly setup cookies so that the user can auto-login to the site from thier own computer...they could set it as their homepage. My friend was trying to get to a megatokyo comic today at school, but there were so many, he couldn't find the one he was looking for, but he had it bookmarked at home and a site like this would have fixed that problem. Maybe you could set it up so that you could just import the list of favorites from your browser, thereby avoiding having to type in all the URLs. I think a site of this sort could be very popular because almost everyone has wanted to go to a site on another computer that they had bookmarked on their own computer, but can't remember the URL.

HeyMr.HockeyJockyBob,

Great idea! I'll think about it. Actually . . . it isn't bad! I could use that.

TROGDOR
the BURNiNATOR !!!

EDIT: Looking for a good name for it. :)

I don't recall what it was called, but Netscape offered something very simular to that several years ago. I'm not sure if they still do.
There was a setting in the Netscape options that allowed you to store your settings and favorites on a network, so a user's multiple computers could share the same set of favorites.

It's still a good idea... Go ahead and burninate the countryside.

Quote:

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Originally posted by Hey15Bob
I thought of something today that I'm not sure has ever been done. What about a website where people can go and store a list of favorites....

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Search google for "online bookmarks".
http://www.backflip.com/
http://www.mybookmarks.com/
http://murl.com/
http://webfavorites.com/

I used to use a site like this a couple years ago. I quit using it though. It's only really useful if you connect using public computers or have a lot of your own computers.

I go to a school where there are quite a few people quit adept at programming, but I offer this challenge: Write your own programming language. The requirements:

1. An executable parser/compiler
2. A wide array of functions and variables
3. Language should be able to handle a majority of programs that C/C++ can handle
4. Must be able to run on both Linux and Windoze
5. Simple syntax

Maybe the "JL" language could come out of here. Start coding :)

Quote:

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Originally posted by grady
swap two integers without using a temporary variable.

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Here is my version in LISP. It's my first LISP program, so go easy on me.;)

Code:

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(setq lis (list 3 8))
(setq lis
  (list
      (second lis)
      (first lis)))

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I put both numbers into one list, and that let me do it with only one data type. Hope that's legal.:p

If you're going to write your own programming language, take a look at flex and bison to help you. Linux Format (in the UK) has been running a great series on creating a programming language for several issues now, and flex and bison are what the author uses.

Quote:

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Originally posted by sasKuatch
Here is my version in LISP. It's my first LISP program, so go easy on me.;)

Code:

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(setq lis (list 3 8))
(setq lis
  (list
      (second lis)
      (first lis)))

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I put both numbers into one list, and that let me do it with only one data type. Hope that's legal.:p

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Did anyone post the Python solution to this? It's really neat:

Code:

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a,b = b,a

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Will swap the two :D I was dead impressed when I learnt that (I'm easily pleased)

Code:

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>>> a=100
>>> b=200
>>> a,b=b,a
>>> a
200
>>> b
100
>>>

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In Perl, you'd say:

($a, $b) = ($b, $a);

which must be even cleverer than Python:p

Quote:

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Originally posted by o0zi
In Perl, you'd say:

($a, $b) = ($b, $a);

which must be even cleverer than Python:p

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Is this a joke?

Sure hope so:)

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Originally posted by dchidelf
Go ahead and burninate the countryside.

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Burninating the peasants,
Burninating all the peoples,
IN THEIR THACHED-ROOFED COTTAGES!
thached-roof cottages
And the Trogdor comes in the NIIIGHT!

So, I took mullet's suggestion (a couple pages back now) and decided to try and learn basic python by way of hangman.
Here is a newbie's attempt at hangman in python.
It meets all of mullet's specs, with the number of guesses excepted.

you run the program
python hangman.txt 'word or phrase for game'

Then just follow the instructions.

the one exception I made was that he wanted:

Quote:

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The user has 2x as many guesses as there are letters in the word to guess the word.

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I won't tell you why I made the change, but if you play the game, you'll see soon enough.

I welcome any and all comments/suggestions/complaints about my program. Since I'm a newbie at this, I consider it all constructive criticism.
enjoy!
-nathan

p.s. oh yeah, and I think my next project will be a program that will keep track of a darts game of cricket for 2 or 3 players. we were playing darts the other night, and could've used it. so, if anyone else is up for it, that's my idea for a 'newbie challenge' maybe I'll get *****ious and learn some gui stuff too......

OK - played the game now. Couple of comments to make:

1. It only accepts a single word, not a whole phrase - if you put in something like 'star wars' it only takes the first word.

2. It includes the quotes you put in - ie from the above it will actually take 'star as the word

My suggested solution would be to start the game by asking them to enter a word or phrase, rather than using it as an argument for the program.

Other than that, good job! :D

Mr. Ben,
when I play it on my computer, it seems to work as expected

for example:

Quote:

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[friedn@localhost programming]$ python hangman.txt 'some stuff'
**** *****
Please enter a guess:

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and the final line would be:

Quote:

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Please enter a guess: f
some stuff

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I believe you that it's different on your machine, but I don't know why. Any ideas on why?

perplexing...........
-nathan

Probably because I'm running it at work under Windows........

Yeah, works fine for me. Probably has to do with how DOS (I'm guessing) takes in command like arguments. I don't think it recognizes single quotes. Try double quotes, mrBen.

Quote:

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Originally posted by sasKuatch
Yeah, works fine for me. Probably has to do with how DOS (I'm guessing) takes in command like arguments. I don't think it recognizes single quotes. Try double quotes, mrBen.

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Aha!

That worked. :D

I retract all my previous comments.

Here's another answer to that square question I asked a while ago:

Code:

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#include <iostream>

int main() {
        int square(1), diff(3);
        while (square < 10000) {
                std::cout << square << std::endl;
                square += diff;
                diff += 2;
        }
}

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Ok, new challange, this one is basically a little parser with little to do with math. Mostly strings.

Convert an IP address to a unsigned long(32-bit) and back.

Criteria:

1. The only functions you can use, you have to create yourself, no using libraries.

2. The IP address can be given to you in any format, doesn't have to be XXX.XXX.XXX.XXX, it can also be XXX.XX.XX.XXX or anything else.

I hope that's enough to discourage any "cheaters" ;)

OK - this is a 5 minutes Python beginning (I'm at work - don't have any more time). It converts an IP address to a 32bit (unsigned) hex number.

It doesn't convert back yet, but it would take an IPv6 address ;)

Code:

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#!/usr/bin/python

ip="192.168.1.10"

hexip=[hex(int(x))[2:] for x in ip.split('.')]

for loop in range(len(hexip)):
    if len(hexip[loop])==1:
          hexip[loop]="0"+hexip[loop]

print "".join(hexip)

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Nice Mr. Ben, but aren't split, len and range functions? I'll let it slide though. :) Aren't there any C/C++/JAVA programers who want to represent?

Ok, next. Now we have our IP address in unsigned long form and string form.

Let's say a user says that he/she wants to increment the value of part of the ip address by pointing at a position in the string and incrementing it there. (The ip string is now always XXX.XXX.XXX.XXX)

I.E. "192.168.001.010"
^
changes to

"202.168.001.010"

But when the user would select 1 from 192, it doesn't increment since 292 is out of range.

So here's kinda how it'll work,

OUTPUT: 192.168.001.010
INPUT: index of decimal user wishes to increment
OUTPUT: 202.168.001.010

In the background, you'll have the IP address stored in a unsigned long/int (32-bit) and only convert to string to output.

The REAL challange: Write it in a few lines as you can without using ANY functions(other than those you create)

P.S. Getting these challanges from portions of code I write at work, in case someone might think is hw or something. I did this the actual work, not i/o, in 6 lines of code.

[edit]speaking of work, maybe i should do some...[/edit]

Quote:

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Originally posted by tecknophreak
Nice Mr. Ben, but aren't split, len and range functions? I'll let it slide though. :)

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Yeah, but so are hex and int. But they are all builtins, so it's not like he's using a library or something.

Also, mrBen, yours wouldn't take an ipv6 address and do it because those use ':' as the separator and not '.' ;) I actually think I posted the code to do just this very challenge on this board (or somewhere) not too long ago.

Quote:

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Originally posted by tecknophreak
Aren't there any C/C++/JAVA programers who want to represent?

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Calling me out?
Heheh. I would, but I just accidentally deleted my whole hd. Partitioning error without backing up. (I know, I know... stupid idea) :D

I'm gonna be spending the next few days setting up my new Knoppix/Debian system. If no one has come up with anything, then I'll give it a shot.

While I'm here, I might as wel post another challenge. How about something simple :):
Create a program that inputs a file, replaces all tabs with 3 spaces, and outputs it to another file.

yes i am!

Quote:

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Originally posted by Sepero
While I'm here, I might as wel post another challenge. How about something simple :):
Create a program that inputs a file, replaces all tabs with 3 spaces, and outputs it to another file.

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Another moment to stretch my Python fingers again: (Amendments from Strike to follow ;) )

Code:

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#!/usr/bin/python

import os, re

inputfile="/home/mrben/input.txt"
outputfile="/home/mrben/output.txt"

data=(open(inputfile,'r').read())
output=open(outputfile,'w')

output.write(re.sub('\t','  ',data)

output.close()

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(Strike - could you tell me whether a file gets automatically closed if you read it as part of the open statement, and if not, how to close it?)

You could, of course, implement this in a single Python line from the Python prompt (having imported the relevant libraries)

Code:

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open('/home/mrben/output.txt','w').write(re.sub('\t','  ',(open('/home/mrben/input.txt','r').read())))

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....but you wouldn't want to do that ;)

You can do whole thing in one line if you want.

Code:

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file('/home/mrben/output.txt','w').write(__import__('re').sub('\t','  ',(file('/home/mrben/input.txt','r').read())))

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Notes: use file, not open. Also, if you want to make it neater, you could have something like a NUM_SPACES constant variable and then just sub it with ' ' * NUM_SPACES :)

Quote:

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Originally posted by Strike
You can do whole thing in one line if you want.

Code:

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file('/home/mrben/output.txt','w').write(__import__('re').sub('\t','  ',(file('/home/mrben/input.txt','r').read())))

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Notes: use file, not open. Also, if you want to make it neater, you could have something like a NUM_SPACES constant variable and then just sub it with ' ' * NUM_SPACES :)

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Cheers Strike; knew I could rely on you :D

Python Rocks!

Here is the perl way to the replace tab with three spaces challenge.
Other than opening the file, basically one line to replace and one to write to file.

Code:

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#! /usr/sbin/perl

open (INFILE, "$ARGV[0]") or die "Cannot open file: $ARGV[0] $!";
open (OUTFILE, "> $ARGV[1]") or die "Cannot open file: $ARGV[1] $!";


while(<INFILE>) {
  $_ =~ s/\t/  /g;
  print OUTFILE "$_";
}

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Here is the perl code for the ip parser challenge:

Code:

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#! /usr/sbin/perl

$ip="123.234.21.123";
my $iplong;
my $ip2;
my $delim;
my @len;

if($ip =~ /(\d{2,3})(\.|:)(\d{2,3})(\.|:)(\d{2,3})(\.|:)(\d{2,3})/) {
  $iplong = $1 . $3 . $5 . $7;
  $delim = $2;
 
  if($1/100 >= 1) {$len[0] = 3;} else {$len[0] = 2;}
  if($3/100 >= 1) {$len[1] = 3;} else {$len[1] = 2;}
  if($5/100 >= 1) {$len[2] = 3;} else {$len[2] = 2;}
  if($7/100 >= 1) {$len[3] = 3;} else {$len[3] = 2;}

  print "$iplong\n";
}

if($iplong =~ /\b(\d{$len[0]})(\d{$len[1]})(\d{$len[2]})(\d{$len[3]})\b/) {
  $ip2 = $1 . $delim . $2 . $delim . $3 . $delim . $4;
  print "$ip2\n";
}

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Ok, I might make a fool of myself giving such a simple challenge, but I'm no guru.

Write a program to compute 253 to the 9427th power (or other such ridiculously large numbers).

I've attached the answer, no cheating now!

Okay... I've been working on this for a couple of days now, more off than on. It's a simple pattern matching sort of thing I call MatchScrabble. It works as follows:

A user enters a String of scrambled characters such as "garmrop." The application loads a wordList (a flat file in this case) against which it must find a possible matching word. The basic idea is to unscramble the word and see if exists in the word list. To continue the example -- say we have a wordList constructed as follows:
---------
program
entry
situation
telling
stop
progrom
tron
more
vortex
teeth
seriously
poor
people
pudding
stopping
starting
eating
drinking
--------

The user enters the string "garmrop." The application should attempt to find a match for this in the word list. In this case the match would be on the first entry: "program" so your app, given that input against that wordList, should return a match on the word 'program.' I'd like to make it efficient enough so that it scales to very long wordLists, eventually using the entries in the Oxford English Dictionary as the wordList.

Simple, right?

Quote:

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Originally posted by Sepero
Calling me out?
Heheh. I would, but I just accidentally deleted my whole hd. Partitioning error without backing up. (I know, I know... stupid idea) :D

I'm gonna be spending the next few days setting up my new Knoppix/Debian system. If no one has come up with anything, then I'll give it a shot.

While I'm here, I might as wel post another challenge. How about something simple :):
Create a program that inputs a file, replaces all tabs with 3 spaces, and outputs it to another file.

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Though this doesn't really fit into the programming challenge I'd use sed to accomplish this:

cat $file |sed 's/[TAB]/[3SPACES/' > $newfile

Sometimes the best programming is using the tools already present :)

#!/usr/bin/perl -w

while(<>) {
s/\t/ /;
print;
}

Quote:

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Originally posted by hotleadpdx
cat $file |sed 's/[TAB]/[3SPACES/' > $newfile

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You don't even need to use cat for that (this is one of the Useless Uses of Cat, congratulations! :p)

You can do this instead:

sed -e 's/[TAB]/[3 SPACES]/' <$file >$newfile

Or, better yet, do it in-place (only works with recent versions of sed):

sed -i -e 's/[TAB]/[3 SPACES]/' $file

"Useless Uses of Cat" :) How amusing :) Where's the list kept? Using cat is a bad habit of mine from working with compressed files all day (zcat $file | blah blah...). But! If there's a sed command line option that allows it to read a compressed file I'll change my ways :)

Quote:

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Originally posted by Ratboy68
Okay... I've been working on this for a couple of days now, more off than on. It's a simple pattern matching sort of thing I call MatchScrabble. It works as follows:

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I cheated and used /usr/shared/dict/words as the dictionary, it can be modified to look where ever it wants, just add a -f /location to the args and look for it.

[edit]I don't want to hear anyone yelling at me about using "using namespace std;", cause it's just a little prog[/edit]

Quote:

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Originally posted by tecknophreak
[edit]I don't want to hear anyone yelling at me about using "using namespace std;", cause it's just a little prog[/edit]

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Aww, come on! I want to yell at you about it! (... or, uh, something...)

:p

Quote:

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Originally posted by hotleadpdx
"Useless Uses of Cat" :) How amusing :) Where's the list kept?

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http://rhols66.adsl.netsonic.fi/era/unix/award.html ;)