TweetFollow Us on Twitter

Aug 93 Challenge
Volume Number:9
Issue Number:8
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.

REPLACE ALL

Have you ever done a Replace All operation in some program and thought that it was taking more time than it should to do the job? Well, this month you’ll have your chance to show those text-based applications how to do it right. The goal is to write a case-sensitive find and replace function.

The prototype of the function you write is:

long ReplaceAll(sourceHndl, 
 replaceHndl, targetHndl)
Handle  sourceHndl;
Handle  replaceHndl;
Handle  targetHndl;

The sourceHndl contains the text to search for. The replaceHndl contains the text to replace the source text with, once found, and the targetHndl contains the text to look in. You should replace each occurance of the sourceHndl text in targetHndl with the replaceHndl text. You can get the sizes of each piece by using GetHandleSize. And you can resize targetHndl as necessary with normal Mac memory manager calls.

For example, suppose targetHndl contained this text:

Perhaps this modern sorcery especially attracts those who believe in 
happy endings and fairy godmothers.

with this sourceHndl text:

fairy godmothers

and this replaceHndl text:

pink elephants

After a call to ReplaceAll targetHndl would contain:

Perhaps this modern sorcery especially attracts those who believe in 
happy endings and pink elephants.

The return value from ReplaceAll is the actual number of substitutions made (1 in this example). You must find an exact match before doing a replacement (i.e. ‘cat’ != ‘Cat’). The max size of each Handle on entry to ReplaceAll will be 255 bytes for sourceHndl and replaceHndl; and 65535 bytes for targetHndl. There is no max output size for targetHndl. You should grow or shrink targetHndl as necessary so that it’s exactly the correct size when ReplaceAll returns. If you run out of memory while trying to grow targetHndl then return -1 instead of the number of substitutions. The text you will be searching through will be mixed case English text containing punctuation.

TWO MONTHS AGO WINNER

Congratulations to Bob Boonstra (Westford, MA) for his fast and small entry in the Where In The World challenge. Tying Bob for speed but not for code size is Jeff Mallett (Hickory, NC). Jeff’s solution was a little faster than Bob’s for some cases and a little slower than Bob’s for others. I couldn’t find a pattern so I went to the second criteria, code size, to pick the winner.

Here are the sizes and times for the 16 entries that yielded correct results:

Name bytes ticks

Bob Boonstra 358 55

Jeff Mallett 728 55

Stepan Riha 514 78

Jim Bumgardner 454 86

Jeff Tupper 624 94

Russ LaValle 530 101

Jan Bruyndonckx 402 112

David Salmon 638 133

Ted Krovetz 250 136

Patrick Breen 350 137

Ricky Schrieber 286 145

Thomas Studer 488 164

Stuart McIntosh 390 230

Robert Fisher 396 268

David Rand 302 420

Bob Menteer 1224 506

Since the puzzle stated that exact matches would be passed to FindCity 2/3rds of the time it is reasonable to do an exact match search first, before starting off and trying to find the five closest matches. Bob makes this first pass by comparing the first 4 bytes of the target string with the first 4 bytes of each element in the cities array. Only if there is an exact match (which includes the length byte) does he then continue to check the remaining parts of the string (again, 4 bytes at a time through clever typecasting).

Once Bob detects that he doesn’t have an exact match, he calculates a closeness-of-match number for every entry in the cities array. But he eliminates some of the work by first comparing the difference in length bytes between the target string and the current element. If it’s greater than his current largest difference (of the 5 closest he’s keeping track of) then he skips the element completely and moves on to the next. This is a neat trick that takes advantage of the way the closeness-of-match number was defined. I like it.

Here’s Bob’s winning solution:

/* FindCity by Bob Boonstra */
 
#define kMax5
#define kSentinal0x035A5A5A
#define low3Bytes0x00FFFFFF
 
typedef struct distRec {
 short  theDist;
 unsigned short  theIndx;
} distRec;

Boolean FindCity(cityNames, cityToFindNamePtr, 
 closestMatches)
Str255  cityNames[];
Str255  *cityToFindNamePtr;
unsigned short closestMatches[];
{
 distRectheRec[kMax];
 unsigned char   *curCityP, *city2Find;
 unsigned short  curIndx;
 register short  maxDist;
  
 city2Find = *cityToFindNamePtr;
 curCityP = cityNames[0];
 /*
  *Scan for an exact match.
  */
 {
 register long toFind3;

 curIndx = 0;
 toFind3 = *(long *)city2Find & low3Bytes;
 do {
 if ( *(long *)curCityP == *(long *)city2Find ) {
 /*
  *If first 4 characters match, look at the
  *rest in chunks of 4 characters.
  */
 register short charsLeft;
 register unsigned char *s1 = curCityP+4;
 register unsigned char *s2 = city2Find+4;

 if ( (charsLeft = *curCityP-7) >= 0 ) {
 do {
 if ( *(long *)s1 != *(long *)s2 )
 goto nextOne;
 s1 += 4;  s2 += 4;
 } while ( (charsLeft-=4) >= 0 );
 }
 /*
  *If all chunks of 4 characters match, look at the
  *rest individually.
  */
 if (charsLeft+=4) {
 do {
 if (*s1++ != *s2++)
 goto nextOne;
 } while (--charsLeft);
 }
 /*
  *Exact match found.  Return index of match.
  */
 closestMatches[0] = curIndx;
 return(1);
 /*
  *Process the next city. Exit if it is greater in
  *alphabetic order (based on 1st 3 characters,
  *w/o length byte).
  *Sentinal will force exit if necessary.
  */
 nextOne: ;
 }

 ++curIndx;
 curCityP+=sizeof(Str255);

 }  while ( (*(long *)curCityP & low3Bytes) <= toFind3 );
 }
 /*
  *Initialize distance structure for 5 closest matches.
  */
 noMatch:
 {
 register distRec *p = &theRec[0];

 (++p)->theDist = (++p)->theDist = (++p)->theDist =
 (++p)->theDist = (p)->theDist = maxDist = 255;
 }
 /*
  *Loop thru cityNames to find closest matches.
  */
 curCityP=cityNames[0];
 curIndx=0;
 do {
 register short curDist;
 /*
  *Calculate dist between cityToFind and cityName[curIndx].
  */
 {
 register unsigned char *s1,*s2;
 register short lng;

 /*initialize dist to length difference */
 s2 = city2Find;
 lng = *s2++;
 if ((curDist = *(s1=curCityP) - lng) < 0) {
 curDist = -curDist;
 lng = *s1;
 }
 /*
  *Move to next city if distance exceeds the distance
  *of 5 other cities.
  *Increment dist for each nonMatching char.
  *Unroll for a little extra speed.
  */
 ++s1;
 do {
 if (*s1++ != *s2++)
 if (++curDist >= maxDist) goto nextCity;
 if (!(--lng)) break;
 if (*s1++ != *s2++)
 if (++curDist >= maxDist) goto nextCity;
 if (!(--lng)) break;
 if (*s1++ != *s2++)
 if (++curDist >= maxDist) goto nextCity;
 if (!(--lng)) break;
 if (*s1++ != *s2++)
 if (++curDist >= maxDist) goto nextCity;
 } while (--lng);
 }
 /*
  *This city is closer than at least one of the five
  *currently closest cities.  Store the distance and
  *the index in the proper place.
  *distRec[0].theIndx is the closest match, and
  *distRec[0].theDist is the associated distance
  */
 {
 register distRec *q=theRec+kMax-1;

 maxDist=curDist;
 if (curDist >= (q-1)->theDist) goto storeIt;
 *q = *(q-1);
 maxDist = q->theDist;  --q;  /* [3]-->[4] */
 if (curDist >= (q-1)->theDist) goto storeIt;
 *q = *(q-1);  --q;           /* [2]-->[3] */
 if (curDist >= (q-1)->theDist) goto storeIt;
 *q = *(q-1);  --q;           /* [1]-->[2] */
 if (curDist >= (q-1)->theDist) goto storeIt;
 *q = *(q-1);  --q;           /* [0]-->[1] */
 storeIt:
 q->theDist = curDist;
 q->theIndx = curIndx;
 }
 /*
  *Process next city.
  */
 nextCity:
 curCityP+=sizeof(Str255);
 ++curIndx;
 /*
  *Exit when sentinal is found.
  */
 } while (*(long *)curCityP != kSentinal);

 /*
  *Return indices of 5 closest cities.
  */
 {
 register unsigned short *p = closestMatches;
 register unsigned short *q = &theRec[0].theIndx;

 *p++ = *q;  q+=2;
 *p++ = *q;  q+=2;
 *p++ = *q;  q+=2;
 *p++ = *q;  q+=2;
 *p   = *q;
 }
 return(0);
}

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). Only pure C code can be used. Any entries with any assembly in them will be disqualified. 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. All code should be limited to 60 characters wide. This will aid us in dealing with e-mail gateways and page layout.

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, CompuServe: 71552,174 and America Online: MT PRGCHAL. 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

Quicken 4.6.3 - Complete personal financ...
Quicken makes managing your money easier than ever. Whether paying bills, upgrading from Windows, enjoying more reliable downloads, or getting expert product help, Quicken's new and improved features... Read more
Smultron 10.0 - Easy-to-use, powerful te...
Smultron 10 is an elegant and powerful text editor that is easy to use. You can use Smultron 10 to create or edit any text document. Everything from a web page, a note or a script to any single piece... Read more
Apple Numbers 4.3 - Apple's spreads...
With Apple Numbers, sophisticated spreadsheets are just the start. The whole sheet is your canvas. Just add dramatic interactive charts, tables, and images that paint a revealing picture of your data... Read more
Apple Pages 6.3 - Apple's word proc...
Apple Pages is a powerful word processor that gives you everything you need to create documents that look beautiful. And read beautifully. It lets you work seamlessly between Mac and iOS devices, and... Read more
Opera 47.0.2631.83 - High-performance We...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more
BetterTouchTool 2.304 - Customize multi-...
BetterTouchTool adds many new, fully customizable gestures to the Magic Mouse, Multi-Touch MacBook trackpad, and Magic Trackpad. These gestures are customizable: Magic Mouse: Pinch in / out (zoom... Read more
Drive Genius 5.0.5 - $49.50 (50% off)
Drive Genius features a comprehensive Malware Scan. Automate your malware protection. Protect your investment from any threat. The Malware Scan is part of the automated DrivePulse utility. DrivePulse... Read more
Apple Configurator 2.5 - Configure and d...
Apple Configurator makes it easy to deploy iPad, iPhone, iPod touch, and Apple TV devices in your school or business. Use Apple Configurator to quickly configure large numbers of devices connected to... Read more
Apple Keynote 7.3 - Apple's present...
Easily create gorgeous presentations with the all-new Keynote, featuring powerful yet easy-to-use tools and dazzling effects that will make you a very hard act to follow. The Theme Chooser lets you... Read more
Vivaldi 1.12.955.36 - An advanced browse...
Vivaldi is a browser for our friends. In 1994, two programmers started working on a web browser. Our idea was to make a really fast browser, capable of running on limited hardware, keeping in mind... Read more

Another Lost Phone: Laura's Story...
Another Lost Phone: Laura's Story 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Another Lost Phone is a game about exploring the social life of a young woman whose phone you have just... | Read more »
The Witness (Games)
The Witness 1.0 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0 (iTunes) Description: You wake up, alone, on a strange island full of puzzles that will challenge and surprise you. You don't remember who you are, and... | Read more »
Egg, Inc. guide - how to build your gold...
Egg, Inc.'s been around for some time now, but don't you believe for one second that this quirky clicker game has gone out of style. The game keeps popping up on Reddit and other community forums thanks to the outlandish gameplay (plus, the... | Read more »
The best deals on the App Store this wee...
Good news, everyone! Your favorite day of the week has arrived at last -- it's discount roundup day! This fine Wednesday evening we're gathering up the hottest deals on the App Store. We've got action platformers, we've got puzzle games, we've got... | Read more »
Morphite (Games)
Morphite 1.08 Device: iOS Universal Category: Games Price: $7.99, Version: 1.08 (iTunes) Description: | Read more »
Fitness AR (Healthcare & Fitness)
Fitness AR 0.1.1 Device: iOS Universal Category: Healthcare & Fitness Price: $2.99, Version: 0.1.1 (iTunes) Description: Explore your Strava bike rides and runs in augmented reality. A beautiful 3D terrain map, powered by Mapbox... | Read more »
ARise (Games)
ARise 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: **ARKit only Puzzle game****Chapter 1 available now - More worlds coming soon!** ARise is an experience about perspective. Using the AR... | Read more »
The best games to play while you wait fo...
SteamWorld Dig 2 is out this week on PC and Switch, and people are understandably excited. This clever series by Image and Form combines our favorite metroidvania mechanics with an esquisite universe, excellent storytelling, and true wit. While... | Read more »
Drag'n'Boom beginner's gu...
Have you ever wanted to burn and pillage a village as a bloodthirsty dragon? If you answered yes to that question, Drag'n'Boom offers you the perfect chance to do so, casting you as an adorable little dragon that wants to set humankind aflame. It... | Read more »
Thimbleweed Park (Games)
Thimbleweed Park 1.0.0 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0.0 (iTunes) Description: A brand new adventure game from Ron Gilbert and Gary Winnick, creators of the classics Monkey Island and Maniac Mansion!... | Read more »

Price Scanner via MacPrices.net

Apple restocks Certified Refurbished 13-inch...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $719 and 2016 models available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Is iPhone X Really The Future Of The Smartpho...
Should iPhone X even be called a telephone? It does of course support telephony and texting, but its main feature set is oriented to other things. It is also debatable whether it makes any rational... Read more
OtterBox Announces Full Case Lineup for iPhon...
Apple revolutionized the smartphone industry 10 years ago with the original iPhone, and OtterBox has set the standard of protection from the very beginning by protecting every generation of iPhone.... Read more
LifeProof Introduces What’s NEXT Cases for iP...
LifeProof built its reputation on sleek, ultra-protective iPhone cases. From 360-degree coverage to the first screenless waterproof case, the protection pioneer has always pushed the limits.... Read more
Apple Refurbished 2016 15-inch MacBook Pros a...
Apple has Certified Refurbished 2016 15″ Touch Bar MacBook Pros available starting at $1949. An Apple one-year warranty is included with each model, and shipping is free: – 15″ 2.7GHz Touch Bar Space... Read more
Wednesday deal: 15-inch MacBook Pros for up t...
B&H Photo has 2017 15″ MacBook Pros on sale for $150-$200 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray: $2199, $200 off MSRP... Read more
2.6GHz Mac mini on sale for $599, $100 off MS...
B&H Photo has the 2.6GHz Mac mini (MGEN2LL/A) on sale for $599 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Snag a 15-inch 2.2GHz Retina MacBook Pro, App...
Apple has Certified Refurbished 2015 15″ 2.2GHz Retina MacBook Pros available for $1699. That’s $300 off original MSRP, and it’s the lowest price available for a 15″ MacBook Pro currently offered by... Read more
Apple Refurbished 3TB Time Capsule for $279,...
Apple has Certified Refurbished 3TB Time Capsules available for $279 including free shipping plus Apple’s standard one-year warranty. Their price is $120 off MSRP. Read more
19% off Smart Battery Cases for iPhone 7
Amazon has both Black and White Smart Battery Cases for iPhone 7s available for $80.41 including free shipping. Their price is $18.59, or 19%, off MSRP. Read more

Jobs Board

Full time *Apple* Hardware Tech needed - ma...
…high level of attention to detail Ethics, integrity and trust Be a geek & Previous Apple experience a must. Previous Apple Retail or other Apple Specialist Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
*Apple* Store - Technical Specialist - Apple...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* News Product Marketing Mgr., Publish...
Job Summary The Apple News Product Marketing Manager will work closely with a cross-functional group to assist in defining and marketing new features and services. Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.