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.

 
AAPL
$100.96
Apple Inc.
-0.83
MSFT
$47.52
Microsoft Corpora
+0.84
GOOG
$596.08
Google Inc.
+6.81

MacTech Search:
Community Search:

Software Updates via MacUpdate

Airfoil 4.8.9 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
WhatRoute 1.13.0 - Geographically trace...
WhatRoute is designed to find the names of all the routers an IP packet passes through on its way from your Mac to a destination host. It also measures the round-trip time from your Mac to the... Read more
Chromium 37.0.2062.122 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. FreeSMUG-Free OpenSource Mac User Group build is... Read more
Attachment Tamer 3.1.14b9 - Take control...
Attachment Tamer gives you control over attachment handling in Apple Mail. It fixes the most annoying Apple Mail flaws, ensures compatibility with other email software, and allows you to set up how... Read more
Duplicate Annihilator 5.0 - Find and del...
Duplicate Annihilator takes on the time-consuming task of comparing the images in your iPhoto library using effective algorithms to make sure that no duplicate escapes. Duplicate Annihilator detects... Read more
jAlbum Pro 12.2 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code!... Read more
jAlbum 12.2 - Create custom photo galler...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results Simply drag and drop photos into groups, choose a design... Read more
Quicken 2015 2.0.4 - Complete personal f...
Quicken 2015 helps you manage all your personal finances in one place, so you can see where you're spending and where you can save. Quicken automatically categorizes your financial transactions,... Read more
iMazing 1.0 - Complete iOS device manage...
iMazing (formerly DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and... Read more
Xcode 6.0.1 - Integrated development env...
Apple Xcode is Apple Computer's integrated development environment (IDE) for OS X. The full Xcode package is free to ADC members and includes all the tools you need to create, debug, and optimize... Read more

Latest Forum Discussions

See All

View Source – HTML, JavaScript and CSS...
View Source – HTML, JavaScript and CSS 1.0 Device: iOS Universal Category: Utilities Price: $.99, Version: 1.0 (iTunes) Description: View Source is an app plus an iOS 8 Safari extension that makes it easy to do one key web developer... | Read more »
Avenged Sevenfold’s Hail To The King: De...
Avenged Sevenfold’s Hail To The King: Deathbat is Coming to iOS on October 16th Posted by Jessica Fisher on September 19th, 2014 [ permalink ] Just in time for Halloween, on October 16 Avenged Sevenfold will be launching | Read more »
Talisman Has Gone Universal – Can Now be...
Talisman Has Gone Universal – Can Now be Played on the iPhone Posted by Jessica Fisher on September 19th, 2014 [ permalink ] | Read more »
Tap Army Review
Tap Army Review By Jennifer Allen on September 19th, 2014 Our Rating: :: SHOOT EM ALLUniversal App - Designed for iPhone and iPad Mindless but fun, Tap Army is a lane-based shooter that should help you relieve some stress.   | Read more »
Monsters! Volcanoes! Loot! Epic Island f...
Monsters! Volcanoes! Loot! | Read more »
Plunder Pirates: Tips, Tricks, Strategie...
Ahoy There, Seadogs: Interested in knowing our thoughts on all this plundering and pirating? Check out our Plunder Pirates Review! Have you just downloaded the rather enjoyable pirate-em-up Plunder Pirates and are in need of some assistance? Never... | Read more »
Goat Simulator Review
Goat Simulator Review By Lee Hamlet on September 19th, 2014 Our Rating: :: THE GRUFFEST OF BILLY GOATSUniversal App - Designed for iPhone and iPad Unleash chaos as a grumpy goat in this humorous but short-lived casual game.   | Read more »
A New and Improved Wunderlist is Here fo...
A New and Improved Wunderlist is Here for iOS 8 Posted by Jessica Fisher on September 19th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Evernote Update for iOS 8 Adds Web Clipp...
Evernote Update for iOS 8 Adds Web Clipping, Quick Notes, and More Posted by Ellis Spice on September 19th, 2014 [ permalink ] | Read more »
Apple Names Ultimate Productivity Bundl...
Apple Names Ultimate Productivity Bundle by Readdle as the Essential Bundle on the App Store Posted by Jessica Fisher on September 19th, 2014 [ permalink | Read more »

Price Scanner via MacPrices.net

Mac Pros available for up to $260 off MSRP
Adorama has Mac Pros on sale for up to $260 off MSRP. Shipping is free, and Adorama charges sales tax in NY & NJ only: - 4-core Mac Pro: $2839.99, $160 off MSRP - 6-core Mac Pro: $3739.99, $260... Read more
13-inch 2.6GHz/256GB Retina MacBook Pros avai...
B&H Photo has the 13″ 2.6GHz/256GB Retina MacBook Pro on sale for $1379 including free shipping plus NY sales tax only. Their price is $120 off MSRP. Read more
Previous-generation 15-inch 2.0GHz Retina Mac...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros now available for $1599 including free shipping plus NY sales tax only. Their price is $400 off original MSRP. B&H... Read more
21″ 2.7GHz iMac available for $1179, save $12...
Adorama has 21″ 2.7GHz Hawell iMacs on sale for $1179.99 including free shipping. Their price is $120 off MSRP. NY and NJ sales tax only. Read more
iOS 8 Adoption Rate Slower than iOS 7, 6, Hit...
Apple began pushing out iOS 8 updates to eligible devices around 1pm ET on September 17, 2014. However, unlike with iOS 7, which boasted a wide variety of differences from its predecessor iOS 6, in... Read more
LIkely Final Definitive OS X 10.9.5 Mavericks...
Apple has released what will almost certainly be the last incremental version number update of OS X 10.9 Mavericks (save for futire security updates) before OS X 10.10 Yosemite is released next month... Read more
Fingerprints, Apple Pay and Identity Theft Wa...
On Sep 9th, CEO Tim Cook unveiled Apple Pay, along with the new iPhone 6 and iWatch. Apple Pay is a newly developed technology that utilizes a near field communication (NFC) to enable customer... Read more
Amazon Introduces Two All-New Kindles
Amazon on Thursday introduced the 7th generation of its Kindle dedicated e-reader device: Kindle Voyage, its top-of-the-line e-reader, and the new $79 Kindle, with a 20% faster processor, twice the... Read more
Save up to $300 on the price of a new Mac wit...
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
13-inch 2.8GHz Retina MacBook Pro available f...
B&H Photo has the new 2014 13″ 2.8GHz Retina MacBook Pro on sale for $1699.99 including free shipping plus NY sales tax only. They’ll also include free copies of Parallels Desktop and LoJack for... Read more

Jobs Board

Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and 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.