TweetFollow Us on Twitter

May 93 Challenge
Volume Number:9
Issue Number:5
Column Tag:Programmers’ Challenge

Programmers’ Challenge

By Mike Scanlin, MacTech Magazine Regular Contributing Author

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

MAGIC ADDITIONS

Thanks to WarrenPM (America Online) for suggesting this month’s Challenge: Find all of the correct addition problems of the form: 123 + 456 = 789 using each of the digits 1 through 9 once each in every solution. For example: 124 + 659 = 783 is true, uses only the digits 1 through 9 and uses each only once.

The prototype of the function you write is:

unsigned short CountMagicAdditions();

You’re not required to produce the actual equations as output, only the correct number of them. Note: This does not mean you should write a separate function that precomputes the answer and then submit a solution that consists of return (kNumMagicAdditions);. Also note that “124 + 659 = 783” and “659 + 124 = 783” are the same thing and only count as 1 magic addition.

Warren says that he wrote a version in AppleSoft BASIC years ago that did lots of string manipulation and took two days to run on his Apple ][. Hopefully your solution in C on my Quadra 700 will run somewhat faster. If you’re really motivated, you could make CountMagicAdditions take a parameter n which would range in value from 3 to 9 and would represent the number of digits used by each equation (and the values of the digits are from 1 to n). For instance: “1 + 2 = 3” is the only solution when n = 3. This more general purpose routine is not required to win the Challenge, though.

TWO MONTHS AGO WINNER

This month we have our first repeat winner of the Programmer’s Challenge. Congratulations to Ronald Nepsund (Northridge, CA) for winning the “Count Unique Words” challenge (Ronald previously won the Travelling Salesman challenge). Close behind, with similar algorithms but slightly different implementations are David Biolsi (Ithaca, NY) and Richard Parker (Irvine, CA).

Here’s a summary of the entries that didn’t crash. The bytes column is the code size, test 1 is the ticks to complete a 17K input file yielding 796 unique words; and test 2 is the ticks to complete a 40K input file yielding 817 unique words (each test was run 20 times and the ticks represent the total time for all instances of each of the two tests):

Name bytes test 1 test 2

Ronald Nepsund 660 63 127

David Biolsi 636 86 146

Richard Parker 386 96 168

Bob Boonstra 856 107 212

JohnnyL 782 124 247

Stepan Riha 418 157 248

Mark Nilsen 588 137 264

Dave Darrah 266 6180 16240

Thank you to all the people who responded to my request for feedback on this column. I will implement as many of your good ideas as I can. The basic feeling was that the challenges are about the right difficulty level as they are but that once in a while a really hard or really easy one might be nice. The vote on Mac-only vs. platform-independent Challenges is split 50/50.

Several people complained about not having enough time to work on the challenge. Neil is working on a way to make the new challenges available electronically before the issue that contains them arrives in your mail box. [Check the online services for more information. See page two for info on which services we support. - Ed.] Hopefully that will help. The other option is to separate the challenge from the solution by three months instead of two. If the electronic option doesn’t help then we may go that route.

I received my second complaint that I don’t provide enough info in the challenge specification to adequately solve it. For instance, in the Count Unique Words challenge one person wondered if he was allowed to overwrite the input buffer or not. Well, I don’t think I’m capable of predicting all such questions up front but I will make more of an effort to eliminate confusion. Also, in the event that I give a less than clear specification, you can always e-mail me at one of the Challenge addresses for clarification (which is probably better than making a really gross wrong assumption and having your entry disqualified).

One question raised by two people that relates to the specification issue is the ANSI compatibility issue and whether or not you’re allowed to make toolbox calls. I had assumed that since this was a Mac magazine people would feel free to call NewPtr instead of malloc (as many who have submitted solutions have done). I guess that was a bad assumption. So, the rules now state that you may make toolbox calls if you want to. There will probably be a Challenge some day that is Mac-specific and requires toolbox interaction but you’re certainly not required to use the toolbox if arriving at the solution doesn’t necessitate it (do whatever is fastest!).

TRAVELLING SALESMAN NOTE

Thanks to Stepan Riha (Austin, TX) for pointing out a further optimization in the Travelling Salesman winning solution. Since you’re not really concerned with the actual distance between points but only the relative distance between points, you don’t need to use square root at all; you can just compare the squares of the distances instead (which is faster). As Stepan says, “A careful analysis of a problem can often improve performance better than careful optimization. Combination of the two gives you truly great code!”

Here’s Ronald’s Count Unique Words winning solution:

/*****************************************************
 * Unique word count by Ronald M. Nepsund
 *
 * The original text is uppercased with all non
 * alphabetic characters turned to zero. The list of
 * unique words works as follows: The word is used to
 * to index into a 1024 entry hash table. The hash
 * table contains pointers to the beginning of a linked
 * list of word entries. Each word entry holds the
 * length of the word and a pointer to the first
 * occurance of the word in the original text. The
 * linked list is ordered first by the length of the
 * words and secondly alphabetically
 ****************************************************/

#define kHashMask0x003FF
#define kHashSize0x00400

typedef struct tNode{
 short  length;
 Ptr    wordPtr;
 struct tNode    *nextNode;
} WordTableRec, *WordTablePtr;


/* compare two strings */
short stringCmp(register short length,
 register char *pnt1,
 register char *pnt2)
{
 while (-length > 0 && *pnt1==*pnt2) {
 pnt1++; pnt2++;
 }
 return *pnt1-*pnt2;
}

unsigned short
CountUniqueWords(Ptr textPtr,
 unsigned short byteCount)
{
 Ptr    endPnt,wordStartPtr;
 register char   *charPnt;
 register long   hash;
 long   count;
 register short  wordLength;
 unsigned short  totalWords = 0;
 short  i,cmp;
 WordTablePtr    *hashTable;
 WordTablePtr    wordTable;
 register WordTablePtr  linkPtr;
 WordTablePtr    last,wordTableEntry;
 char   charTypeTable[256];
 long   *zeroTblPtr;
 //total possable number of words = 16556
 //assuming a maximum size buffer of text
 //I will use a hash table size of 1024
 
 count = 4L * kHashSize;
 //array of (NULL)Ptr’s
 hashTable = (WordTablePtr *) NewPtrClear(count);
 if (hashTable == 0L)
 while (TRUE)
 SysBeep(10); //not enough memory
 
 count = 16556L * sizeof(WordTableRec);
 wordTable = (WordTablePtr) NewPtr(count);
 if (wordTable == 0L)
 while (TRUE)
 SysBeep(10); //not enough memory
 
 //zero out the ‘charTypeTable’
 zeroTblPtr = (long *) &charTypeTable;
 for (i=0; i<64; i++)
 *zeroTblPtr++ = 0;

 //init lookup table used for uppercasing and 
 //identifying non letter characters
 for (i=0;i<26; i++)
 charTypeTable[i+(Byte) ‘A’] =
 charTypeTable[i+(Byte) ‘a’] =
   (char) (i+((Byte) ‘A’));
 
 totalWords = 0;
 charPnt = textPtr;
 endPnt = textPtr + byteCount;
 while (charPnt < endPnt) {
 //skip spaces
 while (charPnt < endPnt &&
   charTypeTable[*charPnt] == 0)
 charPnt++;
 //pointer to begining of new word
 wordStartPtr = charPnt;  
 hash = 0;
 if (endPnt-charPnt > 255) {
 //at least 255 characters left
 //advance to the end of the word
 //we can assume that a word is <=255 characters long
 //uppercasing the text
 //and doing a hash function
 while (*charPnt = charTypeTable[*charPnt])
 hash = (hash << 4)  + *charPnt++ - 
 ‘A’ + (hash >> 10);
 }
 else {
 while (charPnt < endPnt &&
   (*charPnt = charTypeTable[*charPnt]))
 hash = (hash << 4) + *charPnt++ - ‘A’ + (hash >> 10);
 }
 wordLength = charPnt-wordStartPtr;

 hash &= kHashMask;
 linkPtr = (WordTablePtr) hashTable[hash];
 
 last = NULL;
 if (linkPtr==NULL) {
 //this hash entry has not been used yet
 wordTableEntry = &wordTable[totalWords++];
 hashTable[hash] = wordTableEntry;
 wordTableEntry->length   = wordLength;
 wordTableEntry->wordPtr  = wordStartPtr;
 wordTableEntry->nextNode = 0;
 }
 else {
 //the entries are ordered by word length
 //find the first entry that is as long or longer
 while (linkPtr != NULL && linkPtr->length < wordLength)
 {
 last = linkPtr;
 linkPtr = linkPtr->nextNode;
 }
 if (linkPtr == NULL) {
 //no other entries as long as this one
 wordTableEntry = &wordTable[totalWords++];
 if (last == NULL)
 hashTable[hash] = wordTableEntry;
 else
 last->nextNode = wordTableEntry;
 wordTableEntry->length = wordLength;
 wordTableEntry->wordPtr= wordStartPtr;
 wordTableEntry->nextNode= NULL;
 }
 else if (linkPtr->length > wordLength) {
 //insert betean ‘last’ and ‘linkPtr’
 wordTableEntry = &wordTable[totalWords++];
 if (last == NULL) {
 wordTableEntry->nextNode = hashTable[hash];
 hashTable[hash] = wordTableEntry;
 }
 else {
 wordTableEntry->nextNode = last->nextNode;
 last->nextNode = wordTableEntry;
 }
 wordTableEntry->length = wordLength;
 wordTableEntry->wordPtr= wordStartPtr;
 }
 else {
 //check entries with same word lengths
 while (linkPtr != NULL &&
   linkPtr->length == wordLength &&
   (cmp = stringCmp(wordLength, wordStartPtr,
   linkPtr->wordPtr)) <0) {
 last = linkPtr;
 linkPtr = linkPtr->nextNode;
 }
 if (linkPtr == NULL) {
 //end of list and no match
 wordTableEntry = &wordTable[totalWords++];
 if (last == NULL)
 hashTable[hash] = wordTableEntry;
 else
 last->nextNode = wordTableEntry;
 wordTableEntry->length = wordLength;
 wordTableEntry->wordPtr= wordStartPtr;
 wordTableEntry->nextNode= 0;
 }
 else if (linkPtr->length > wordLength || cmp>0)   
 {
 //insert word entry here
 wordTableEntry = &wordTable[totalWords++];
 if (last == NULL) { //hash table to point here
 wordTableEntry->nextNode = hashTable[hash];
 hashTable[hash] = wordTableEntry;
 }
 else {
 wordTableEntry->nextNode= last->nextNode;
 last->nextNode = wordTableEntry;
 }
 wordTableEntry->length  = wordLength;
 wordTableEntry->wordPtr = wordStartPtr;
 }
 }
 }
 }
 
 DisposePtr((Ptr) hashTable);
 DisposePtr((Ptr) wordTable);
 
 return totalWords;
}

The Rules

Here’s how it works: Each month there will be a different programming challenge presented here. First, you must write some code that solves the challenge. Second, you must optimize your code (a lot). Then, submit your solution to MacTech Magazine (formerly MacTutor). A winner will be chosen based on code correctness, speed, size and elegance (in that order of importance) as well as the postmark of the answer. In the event of multiple equally desirable solutions, one winner will be chosen at random (with honorable mention, but no prize, given to the runners up). The prize for the best solution each month is $50 and a limited edition “The Winner! MacTech Magazine Programming Challenge” T-shirt (not to be found in stores).

In order to make fair comparisons between solutions, all solutions must be in ANSI compatible C (i.e., don’t use Think’s Object extensions). However, you may call any routine in the Macintosh toolbox you want (i.e., it doesn’t matter if you use NewPtr instead of malloc). All entries will be tested with the FPU and 68020 flags turned off in THINK C. When timing routines, the latest version of THINK C will be used (with ANSI Settings plus “Honor ‘register’ first” and “Use Global Optimizer” turned on) so beware if you optimize for a different C compiler.

The solution and winners for this month’s Programmers’ Challenge will be published in the issue two months later. All submissions must be received by the 10th day of the month printed on the front of this issue.

All solutions should be marked “Attn: Programmers’ Challenge Solution” and sent to Xplain Corporation (the publishers of MacTech Magazine) via “snail mail” or preferably, e-mail - AppleLink: MT.PROGCHAL, Internet: progchallenge@xplain.com, and CompuServe: 71552,174. If you send via snail mail, please include a disk with the solution and all related files (including contact information). See page 2 for information on “How to Contact Xplain Corporation.”

MacTech Magazine reserves the right to publish any solution entered in the Programming Challenge of the Month and all entries are the property of MacTech Magazine upon submission. The submission falls under all the same conventions of an article submission.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

LibreOffice 4.4.1.2 - Free, open-source...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
Freeway Pro 7.0.3 - Drag-and-drop Web de...
Freeway Pro lets you build websites with speed and precision... without writing a line of code! With its user-oriented drag-and-drop interface, Freeway Pro helps you piece together the website of... Read more
Cloud 3.3.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more
Cyberduck 4.6.5 - FTP and SFTP browser....
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Firefox 36.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and... Read more
Thunderbird 31.5.0 - Email client from M...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
VOX 2.4 - Music player that supports man...
VoxIt just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features & support for all audio formats you should ever need... Read more
A Better Finder Rename 9.46 - File, phot...
A Better Finder Rename is the most complete renaming solution available on the market today. That's why, since 1996, tens of thousands of hobbyists, professionals and businesses depend on A Better... Read more
WALTR 1.0.9 - Drag-and-drop any media fi...
WALTR is designed to make it easy to upload and convert any music or video file to an iPad or iPhone format for native playback. It supports a huge variety of media file types, including MP3, MP4,... Read more
Default Folder X 4.6.14 - Enhances Open...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click on... Read more

Check Out the Trailer for the Upcoming F...
Check Out the Trailer for the Upcoming FINAL FANTASY: Record Keeper Posted by Jessica Fisher on February 26th, 2015 [ permalink ] DeNA and Square Enix have announced that | Read more »
Legacy Quest is an Upcoming Rouge-like T...
Legacy Quest is an Upcoming Rouge-like That’ll Kill the Whole Family Posted by Jessica Fisher on February 26th, 2015 [ permalink ] Nexon Co. | Read more »
Grudgeball: Enter the Chaosphere Review
Grudgeball: Enter the Chaosphere Review By Jordan Minor on February 26th, 2015 Our Rating: :: MUSCLE MENUniversal App - Designed for iPhone and iPad Regular Show gets an above average game.   | Read more »
Action RPG League of Angels – Fire Raide...
Gaia is being invaded by the Devil Prince and the demonic Devil Army at his disposal, and it’s up to you and your avatar to defeat him in League of Angels – Fire Raiders. Raise a mighty army from hundreds of recruitable angel heroes and take the... | Read more »
Burn Rubber on the Ice With a New Cars:...
Burn Rubber on the Ice With a New Cars: Fast as Lightning Update Posted by Jessica Fisher on February 26th, 2015 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
AdVenture Capitalist Review
AdVenture Capitalist Review By Jordan Minor on February 26th, 2015 Our Rating: :: DAS KAPITALUniversal App - Designed for iPhone and iPad An inadvertent Marxist manifesto.   | Read more »
Monster vs Sheep Review
Monster vs Sheep Review By Jennifer Allen on February 25th, 2015 Our Rating: :: SAMEY FUNUniversal App - Designed for iPhone and iPad What Monster vs Sheep lacks in variety it makes up for with stress relieving fun. At least, for a... | Read more »
Is Your Face Ready for the New Outwitter...
Is Your Face Ready for the New Outwitters 2.0 Trailer? Posted by Jessica Fisher on February 25th, 2015 [ permalink ] One Man Left Studios has announced that their turn-based strategy game, | Read more »
HowToFormat Review
HowToFormat Review By Jennifer Allen on February 25th, 2015 Our Rating: :: USEFUL TIPSiPhone App - Designed for the iPhone, compatible with the iPad Making a presentation and want to get it just right? HowToFormat teaches you how... | Read more »
Thermo Diem Review
Thermo Diem Review By Jennifer Allen on February 25th, 2015 Our Rating: :: GETS TO THE POINTUniversal App - Designed for iPhone and iPad Want to know whether it’s warmer or colder tomorrow? That’s precisely what Thermo Diem will... | Read more »

Price Scanner via MacPrices.net

Apple Takes 89 Percent Share of Global Smartp...
According to the latest research from Strategy Analytics, global smartphone operating profit reached US$21 billion in Q4 2014. The Android operating system captured a record-low 11 percent global... Read more
New Travel Health App “My Travel Health” iOS...
Rochester, Minnesota based Travel Health and Wellness LLC has announced that its new iOS app help safeguard the user’s health when traveling abroad — “My Travel Health” is now available on the Apple... Read more
Sale! MacBook Airs for up to $115 off MSRP
B&H Photo has MacBook Airs on sale for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 128GB MacBook Air: $799 100 off MSRP - 11″ 256GB MacBook Air: $999 $100... Read more
15-inch 2.0GHz Retina MacBook Pro (refurbishe...
The Apple Store has Apple Certified Refurbished previous-generation 15″ 2.0GHz Retina MacBook Pros available for $1489 including free shipping plus Apple’s standard one-year warranty. Their price is... Read more
Wither The iPad mini? End Of The Road Imminen...
AppleDailyReport’s Dennis Sellers predicts that the iPad mini is going to be left to wither on the vine, as it were, and then just allowed to fade away — a casualty of the IPhone 6 Plus and other... Read more
Android and iOS Duopoly Owns 96.3% of Smartph...
IDC reports that Android and iOS inched closer to total domination of the worldwide smartphone market in both the fourth quarter (4Q14) and the calendar year 2014 (CY14). According to data from the... Read more
13-inch 2.4GHz Retina MacBook Pro available f...
MacMall has the 2013 13″ 2.4GHz/128GB Retina MacBook Pro available for $999.99 for a limited time. Shipping is free. Their price is $300 off original MSRP, and it’s the only sub-$1000 new Retina... Read more
Save up to $300 on a new Mac, $30 on an iPad,...
Purchase a new Mac or iPad at The Apple Store for Education and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free,... Read more
Mac minis available for up to $75 off MSRP
MacMall has Mac minis on sale for up to $75 off MSRP including free shipping. Their prices are the lowest available for these models from any reseller: - 1.4GHz Mac mini: $459.99 $40 off - 2.6GHz Mac... Read more
WaterField Unveils Versatile Padded Gear Pouc...
San Francisco manufacturer WaterField Design’s new Padded Gear Pouch is a light and handy-sized, yet protective, organizer for every kind of take-along gear: technology, travel, toiletries,... Read more

Jobs Board

*Apple* Solutions Consultant - Retail Sales...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Solutions Consultant (ASC)- Retail S...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
Sr. Technical Services Consultant, *Apple*...
**Job Summary** Apple Professional Services (APS) has an opening for a senior technical position that contributes to Apple 's efforts for strategic and transactional Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.