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.

 
AAPL
$100.86
Apple Inc.
-0.77
MSFT
$46.76
Microsoft Corpora
+0.52
GOOG
$579.95
Google Inc.
+6.85

MacTech Search:
Community Search:

Software Updates via MacUpdate

Capture One Pro 8.0.0.433 - RAW workflow...
Capture One Pro 8 is a professional RAW converter offering you ultimate image quality with accurate colors and incredible detail from more than 300 high-end cameras -- straight out of the box. It... Read more
Adobe Acrobat Pro 11.0.09 - Powerful PDF...
Adobe Acrobat allows users to communicate and collaborate more effectively and securely. Unify a wide range of content in a single organized PDF Portfolio. Collaborate through electronic document... Read more
Adobe Reader 11.0.09 - View PDF document...
Adobe Reader allows users to view PDF documents. You may not know what a PDF file is, but you've probably come across one at some point. PDF files are used by companies and even the IRS to... Read more
iFFmpeg 4.6.1 - Convert multimedia files...
iFFmpeg is a graphical front-end for FFmpeg, a command-line tool used to convert multimedia files between formats. The command line instructions can be very hard to master/understand, so iFFmpeg does... Read more
NTFS 11.3.62 - Provides full read and wr...
Paragon NTFS breaks down the barriers between Windows and OS X. Paragon NTFS effectively solves the communication problems between the Mac system and NTFS, providing full read and write access to... Read more
OS X Yosemite 10.10 DP8 - Developer Prev...
Note: This is a Developer Preview. You must be a registered Apple Mac Developer to download this update. You can also sign up for the free OS X Beta Program to download and preview public beta... Read more
FotoMagico 4.5 - Powerful slideshow crea...
FotoMagico lets you create professional slideshows from your photos and music with just a few, simple mouse clicks. It sports a very clean and intuitive yet powerful user interface. High image... Read more
Screenshot Path 1.2.1 - Change the defau...
Screenshot Path lets you change the folder where OS X saves screenshots. Screenshots are saved by default to the user’s desktop. This is handy for the occasional screenshot but those looking to take... Read more
Fantastical 1.3.16 - Create calendar eve...
Fantastical is the Mac calendar you'll actually enjoy using. Creating an event with Fantastical is quick, easy, and fun: Open Fantastical with a single click or keystroke Type in your event details... Read more
GIMP 2.8.14 - Powerful, free image editi...
GIMP is a multi-platform photo manipulation tool. GIMP is an acronym for GNU Image Manipulation Program. The GIMP is suitable for a variety of image manipulation tasks, including photo retouching,... Read more

Latest Forum Discussions

See All

Zynga Unveils First Look at Looney Tunes...
Zynga Unveils First Look at Looney Tunes Dash! Posted by Ellis Spice on September 16th, 2014 [ permalink ] Be vewy, vewy qwiet. I’m hunting wunners featuwing wabbits, and luckily, it’s duck season wunner season. | Read more »
Guardians on the Go – How to Connect to...
At this point I’m relatively certain most of the country is familiar with Destiny. And for those looking to augment their game a bit, Bungie has changed their Bungie Mobile Companion App to Destiny Companion. | Read more »
Kunin Review
Kunin Review By Jordan Minor on September 16th, 2014 Our Rating: :: SHURIKEN DO ITUniversal App - Designed for iPhone and iPad Kunin is a nervous test of ninja reflexes.   Developer: Dodreams Price: FREE Version Reviewed: 1.0.1... | Read more »
4 KEMCO Titles are Just $0.99 for a Limi...
4 KEMCO Titles are Just $0.99 for a Limited Time Posted by Jessica Fisher on September 16th, 2014 [ permalink ] KEMCO RPGs Destiny Fantasia, Infinite Dunamis, Bonds of the Sk | Read more »
Introducing Flash, the Latest Wearable F...
Introducing Flash, the Latest Wearable Fitness Monitor from Misfit Posted by Jessica Fisher on September 16th, 2014 [ permalink ] The Misfit Flash is the newly-released fitness and sleep monitor from | Read more »
Hyper Trip Review
Hyper Trip Review By Jennifer Allen on September 16th, 2014 Our Rating: :: HYPER TWITCHYUniversal App - Designed for iPhone and iPad Tough and unforgiving, Hyper Trip is a bit like Snake – if Snake was really harsh.   | Read more »
Collectible Card Game Earthcore: Shatter...
Collectible Card Game Earthcore: Shattered Elements is Set to Arrive on iOS in 2015 Posted by Ellis Spice on September 16th, 2014 [ permalink ] Polish developers | Read more »
Boogey Boy Review
Boogey Boy Review By Jennifer Allen on September 16th, 2014 Our Rating: :: PRETTY BUT BASICUniversal App - Designed for iPhone and iPad It looks delightful but lack of Game Center support and more variety really affects the fun... | Read more »
Vizzywig 4K (Photography)
Vizzywig 4K 1.0 Device: iOS iPhone Category: Photography Price: $999.99, Version: 1.0 (iTunes) Description: REQUIRES: iOS 7 on iPhone 5S with 32GB or 64GB. (Do not use iOS 8)The world's FIRST mobile 4K video capture, editing and... | Read more »
The Sleeping Prince Review
The Sleeping Prince Review By Jennifer Allen on September 15th, 2014 Our Rating: :: RESTRICTIVE KINGDOM SAVINGUniversal App - Designed for iPhone and iPad The Sleeping Prince looks and feels great to play, but its lack of peril and... | Read more »

Price Scanner via MacPrices.net

Sprint offers 16GB iPad mini for $199.99 with...
Sprint is offering 1st generation 16GB iPad minis for $199.99 with a 2-year service agreement. Standard MSRP for this iPad is $429. Their price is the lowest available for this model. Read more
2.5GHz Mac mini remains on sale for $549, sav...
B&H Photo has the 2.5GHz Mac mini on sale for $549.99 including free shipping. That’s $50 off MSRP, and B&H will also include a free copy of Parallels Desktop software. NY sales tax only. Read more
Apple refurbished iMacs available for up to $...
The Apple Store has Apple Certified Refurbished iMacs available for up to $300 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free. These are the best prices on... Read more
13″ 2.5GHz MacBook Pro offered for $100 off M...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Free GIMP Professional Grade Graphics App Ver...
The latest 2.8.14 version of the oddly-named GIMP (acronym for: GNU Image Manipulation Program) open source, high-end image editing and creation alternative to Adobe’s Photoshop and refuge from... Read more
Apple Announces Record Pre-orders for iPhone...
Apple has released metrics showing a record number of first day pre-orders of iPhone 6 and iPhone 6 Plus, with over four million sold in the first 24 hours. Demand for the new iPhones exceeds the... Read more
10% off iPhone 6 and 6 Plus Otterbox cases
Get 10% off on popular Otterbox iPhone 6 and iPhone 6 Plus cases at MacMall through September 19th. Use code OTTERBOX10 to see the discount. Read more
15-inch MacBook Pros on sale for up to $125 o...
Amazon has the new 2014 15″ Retina MacBook Pros on sale for up to $125 off MSRP including free shipping: - 15″ 2.2GHz Retina MacBook Pro: $1899.99 save $100 - 15″ 2.5GHz Retina MacBook Pro: $2374... Read more
27-inch 3.2GHz iMac on sale for $1698, $101 o...
Abt has the 27″ 3.2GHz iMac on sale for $1698 including free shipping. Their price is $101 off MSRP. Read more
More To Making A Larger iPad Than Expanded Sc...
CNET’s Ross Rubin has posted a thoughtful analysis of prospects for a larger display iPad Pro, noting that Microsoft and Samsung currently have the large-display touchscreen tablet category to... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.