TweetFollow Us on Twitter

Mar 93 Challenge
Volume Number:9
Issue Number:3
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.

Count Unique Words

Most word processors these days have a Count Words command. The quality in terms of accuracy and speed of these commands varies quite a bit. I tested three leading word processors with a document containing 124,829 characters and got three different answers ranging from 18446 words to 18886 words and times ranging from 4 seconds to 11 seconds. I’m not sure what the correct answer was for that document; it depends on how you define what a word is.

For purposes of this month’s challenge, a word is defined as an unbroken set of one or more letters. The input text will only contain upper and lower case letters a to z, spaces, carriage returns, periods and commas (for a total of 56 possible byte values). No digits, hyphens, tabs, other punctuation, etc. Since counting words using this simplified definition is rather trivial, you’re going to count the number of unique words instead.

The prototype of the function you write is:

unsigned short CountUniqueWords(textPtr, byteCount)
PtrtextPtr;
unsigned short byteCount;

Your function should return the number of unique words (case insensitive) in the input text. The maximum word length for individual words in the input text is 255 characters.

This is my 7th programmer’s challenge that I’ve posed to MacTech readers. I have received approximately very little feedback as to what you think of these challenges. Are they too easy, too hard, too uninteresting, or what? Do you want hard core numerical analysis puzzles (like write a fast sqrt function) or do you want Mac-specific problems (like write a fast TileAndStackWindows function) or are things okay as they are? If you have any ideas for future challenges, please send them in (credit will be given in this column if I use one of your ideas). Thanks.

Two Months Ago Winner

The winner of the “Travelling Salesman” challenge is Ronald Nepsund (Northridge, CA) whose solution was the only one of the five I received which gave correct results. The time intensive part of solutions to this class of problems is the distance between two points calculation, which involves a square root. Ronald uses a precomputed sqrt table for values 0 to 25 to eliminate much of this time.

A couple of people chose the algorithm of “find the closest city to where we currently are and move to that city; repeat until all cities have been visited” which is not correct. An example set of input data that broke everyone but Ronald’s solution is: numCities = 8, startCityIndex = 5, *citiesPtr = {1,1}, {2,1}, {3,1}, {2,2}, {1,3}, {2,3}, {3,3}, {2,4}. If you draw it and work it out by hand (through trial and error) you can see that the minimum path distance is 8.66. There is more than one correct ordering for the optimal path but all of the optimal paths will have that same length.

Here is Ronald’s winning solution to the January Challenge:

//***********************************
// Travelling Salesman 
// by Ronald M. Nepsund

#include <math.h>

#define fracBase 0x20000000

//There are two 32 by 20 arrays of longs
//which together give the distance betwean
//any two cities.
//Instead of using Array[i,j] to access
//the array Array[(i<<5)+j] is used
//and two longs are needed to accurately
//measure the distance betwean cities
//so two arrays of longs are used.
//gDistanceFrac is used to hold the
//fractional part of distance in 1/0x20000000
//of a unit.
long  gDistanceInt[640],
 gDistanceFrac[640];
//these are used to represent a path betwean
//the cities.
Byte  gNextCity[20],gOptPath[20];
//how long is the currently selected best
//path so far.
long  gBestPathLength,gFracBestPathLength;

unsignedshort  gNumCities;
unsignedshort  gStartCityIndex;

//precalculated square root for zero to 25
long  qSquTableInt[] =
 {0,1,1,1,2,2,2,2,2,3,3,3,3,3,3,3,
  4,4,4,4,4,4,4,4,4,
  5,5,5,5,5,5,5,5,5,5,5};
//precalculated square root - fractional part
//in 1/0x20000000 of a whole unit
long  qSquTableFrac[]=
 {0,0,222379212,393016784,0,126738030,
 241317968,346685095,444758425,0,
 87122155,169986639,249162657,
 325102865,398174277,468679365,0,
 66091829,130266726,192682403,
 253476060,312767944,370664138,
 427258795,482635936,0 };

void DoPath(short cityIndex, long InttPathLength,
 long fracPathLength);

//The recursive routien that actually finds
//the shortest path.

void  DoPath(registershort cityIndex,
 long InttPathLength,
 long fracPathLength)
{
 register short  i;
 BooleanlastCity;
 long   offset;
 
 if (fracPathLength > fracBase)  {
 //the fractional value variable has
 //exceeded the value of one whole
 //unit
 InttPathLength += 1;
 fracPathLength -= fracBase;
 }
 
 //Has the path has become longer than the
 //shortest path we have already found?
 if (InttPathLength > gBestPathLength ||
 ((InttPathLength == gBestPathLength) &&
  (fracPathLength >= gFracBestPathLength)))
   return;
 
 //lastCity is used to tell if all the
 //cities have been visited
 lastCity = TRUE;
 //for each city
 for(i = 0; i<gNumCities; i++)
 //if not to same city or already
 //visited city
 if ( i != cityIndex &&
  gNextCity[i] == 0xFF) {
 //not at the end of the path
 lastCity = FALSE;
 //path from city ‘cityIndex’ to ‘i’
 gNextCity[cityIndex] = i;
 //offset into distance arrays
 offset = (cityIndex << 5) + i;
 //go to next city adding the
 //distance to that city to the
 //path length
 DoPath(i,
  InttPathLength+gDistanceInt[offset],
  fracPathLength+gDistanceFrac[offset]);
 } //end if and for
 
 // if this is the last city in the chain and
 // is a shorter path than the previous best
 if ((lastCity) &&
 ((InttPathLength < gBestPathLength) ||
  ((InttPathLength == gBestPathLength) &&
   (fracPathLength < gFracBestPathLength))
   ) ) {
 // make this the current best path
 register long *LPnt1,*LPnt2;
 //this is the current shortest path
 //length now
 gBestPathLength = InttPathLength;
 gFracBestPathLength = fracPathLength;
 //copy path to ‘optPath’
 LPnt1 = (long *)&gNextCity;
 LPnt2 = (long *)&gOptPath;
 for (i= ((3+gNumCities) >> 2); i>0; i-)
 *LPnt2++ = *LPnt1++;
 } else 
 //this city is no longer connected to
 //the next city
 gNextCity[cityIndex] = 0xFF;
}

void InitDistances(unsigned short numCities
 Point *citiesPtr);

//initialize two arrays which will give the
//distance betwean any two cities.
void InitDistances(
 unsigned short numCities,
 Point  *citiesPtr)
{
 short  i,j,offset;
 register long *LPntl1,*LPntF1,
 *LPntI2,*LPntF2;
 long   dist;
 short  deltax,deltay;
 double X;
//The distance from city i to j is the same
//as from city j to i.
//Use pointers into the arrays
//We will add a constant to the pointers to
//step through the array
//instead of doing a multiplication to find
//the wanted entries in the array

 //how far is it betwean any two cities
 for (i=0; i<numCities; i++){
 LPntl1 = gDistanceInt  + i;
 LPntF1 = gDistanceFrac + i;
 offset = i << 5;
 LPntI2 = gDistanceInt  + offset;
 LPntF2 = gDistanceFrac + offset;
 for (j=0; j<=i; j++)
 if (i==j){
 //both pointers are pointing
 //to the same locations in the array
 //distance to the same city is zero
 *LPntI2++ = 0;
 *LPntl1 = 0;  LPntl1 += 32;
 *LPntF2++;
 LPntF1 += 32;
 } else {
 //calculate horizontal and vertical
 //distance betwean city ‘i’ and ‘j’
 deltax = citiesPtr[i].h-
 citiesPtr[j].h;
 deltay = citiesPtr[i].v-
 citiesPtr[j].v;
 //The distance betwean the cities is
 // squareRoot( deltax*deltax +
 // deltay*deltay)
 //Where you can, do multiplications
 //using shorts instead of long’s -
 //They are faster.
 if (-255< deltax && deltax<256)
 if (-255< deltay && deltay<256)
 dist = ((long)(deltax*deltax) + 
 (long)(deltay*deltay));
 else
 dist = ((long)(deltax*deltax) + 
 (long)deltay*deltay);
 else
 if (-255< deltay && deltay<256)
 dist = ((long)deltax*deltax + 
 (long)(deltay*deltay));
 else
 dist = ((long)deltax*deltax + 
 (long)deltay*deltay);

 //do squareRoot
 if (dist <= 25) {
 //use sqrt lookup tables for
 //0 to 25
 *LPntI2++  = *LPntl1 =
 qSquTableInt[dist];
  LPntl1 += 32;
 *LPntF2++  = *LPntF1 =
 qSquTableFrac[dist];
  LPntF1 += 32;
 } else {
        X = sqrt(dist);
 //gDistanceInt[(i<<5) + j] = X;
 //gDistanceInt[(j<<5) + i] = X;
 //integer part of distance
 // between points
 dist = X;
 *LPntl1 = *LPntI2++  = dist;
 LPntl1 += 32;
 
 //gDistanceFrac[i<<5 + j] =
 // (X - dist) * $20000000;
 //gDistanceFrac[j<<5 + i] =
 // (X - dist) * $20000000;
 // fractional part
 dist = (X - dist) * fracBase;
 *LPntF2++  = *LPntF1 = dist;
 LPntF1 += 32;
 }
 }
 }
}

void OptimalPath(unsigned short numCities
 unsigned short startCityIndex,
 Point *citiesPtr,Point *optimalPathPtr);

void OptimalPath(numCities,startCityIndex,citiesPtr,
 optimalPathPtr)
unsigned short numCities;
unsigned short startCityIndex;
Point *citiesPtr;
Point *optimalPathPtr;
{
 register short  i,j;
 long   time,index;
 double X;
 
 //generates the tables for the distances
 //betwean any two cities.
 //This routien takes up most of the time.
 InitDistances(numCities,citiesPtr);
 
 //OxFF means that there is no path from
 //this city to another
 for (i=0; i<numCities; i++)
 //no paths betwean cities
 gNextCity[i] = 0xFF;
 
 gNumCities = numCities;
 gStartCityIndex = startCityIndex;
 //any path done by DoPath will be shorter
 //than this
 gBestPathLength = 0x7FFFFFFF;
 gFracBestPathLength = 0;

 //find the best path
 DoPath(startCityIndex,0,0);  
 
 //put the best path into the form
 //desired for ‘optimalPath’
 j=startCityIndex;
 for(i=0; i<numCities; i++) {
 optimalPathPtr[i] = citiesPtr[j];
 j = gOptPath[j];
 }
}

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. 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
$524.94
Apple Inc.
+5.93
MSFT
$40.01
Microsoft Corpora
-0.39
GOOG
$536.10
Google Inc.
-20.44

MacTech Search:
Community Search:

Software Updates via MacUpdate

Mac DVDRipper Pro 4.1.7 - Copy, backup,...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
PDFpenPro 6.2 - Advanced PDF toolkit for...
PDFpenPro allows users to edit PDF's easily. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Create... Read more
PDFpen 6.2 - Edit and annotate PDFs with...
PDFpen allows users to easily edit PDF's. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Features... Read more
Monolingual 1.5.9 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. It requires a 64-bit capable Intel-based Mac and at least... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Starcraft II: Wings of Liberty 1.1.1.180...
Download the patch by launching the Starcraft II game and downloading it through the Battle.net connection within the app. Starcraft II: Wings of Liberty is a strategy game played in real-time. You... Read more
Sibelius 7.5.0 - Music notation solution...
Sibelius is the world's best-selling music notation software for Mac. It is as intuitive to use as a pen, yet so powerful that it does most things in less than the blink of an eye. The demo includes... Read more
Typinator 5.9 - Speedy and reliable text...
Typinator turbo-charges your typing productivity. Type a little. Typinator does the rest. We've all faced projects that require repetitive typing tasks. With Typinator, you can store commonly used... Read more
MYStuff Pro 2.0.16 - Create inventories...
MYStuff Pro is the most flexible way to create detail-rich inventories for your home or small business. Add items to MYStuff by dragging and dropping existing information, uploading new images, or... Read more
TurboTax 2013.r17.002 - Manage your 2013...
TurboTax guides you through your tax return step by step, does all the calculations, and checks your return for errors and overlooked deductions. It lets you file your return electronically to get... Read more

Latest Forum Discussions

See All

Living Planet - Tiny Planet Videos and P...
Living Planet - Tiny Planet Videos and Photos 1.0 Device: iOS Universal Category: Photography Price: $.99, Version: 1.0 (iTunes) Description: 50% OFF LAUNCH SPECIAL! BUY NOW BEFORE THE PRICE GOES UP... | Read more »
Livescribe 3 Smartpen Review
Made by: Livescribe Price: $149.99 for Livescribe 3 Hardware/iOS Integration Rating: 4.5 out of 5 stars Usability Rating: 4 out of 5 stars Reuse Value Rating: 4.75 out of 5 stars Build Quality Rating: 4.5 out of 5 stars Overall Rating: 4.44 out of... | Read more »
Unpossible Review
Unpossible Review By Carter Dotson on April 17th, 2014 Our Rating: :: RALPH WIGGUM APPROVESUniversal App - Designed for iPhone and iPad Unpossible is much better than its English!   | Read more »
Hitman GO Review
Hitman GO Review By Carter Dotson on April 17th, 2014 Our Rating: :: GO HITMAN, GO!Universal App - Designed for iPhone and iPad Hitman GO is not the obvious way to do a mobile version of the Hitman series, but it’s an incredibly... | Read more »
Monster High Ghouls and Jewels is a Frea...
Monster High Ghouls and Jewels is a Freaky Fashion-Forward Match-3 Puzzler Posted by Rob Rich on April 17th, 2014 [ permalink ] | Read more »
Dinosaur Train A to Z Review
Dinosaur Train A to Z Review By Amy Solomon on April 17th, 2014 Our Rating: :: DINO DETAILSUniversal App - Designed for iPhone and iPad Dinosaur Train A to Z is an educational app about dinosaurs that includes In-App Purchases... | Read more »
Easter Comes to Junk Jack X – Bringing N...
Easter Comes to Junk Jack X – Bringing New Crafts, Chemistry, and More Posted by Rob Rich on April 17th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Call of Cookie Review
Call of Cookie Review By Jordan Minor on April 17th, 2014 Our Rating: :: COOKIE CRUMBLESUniversal App - Designed for iPhone and iPad Call of Cookie proves that plants aren’t the only fighting foods out there.   | Read more »
Corel Launches Video Editing App Pinnacl...
Corel Launches Video Editing App Pinnacle Studio for iPhone, Updates iPad Version for iOS 7 Posted by Tre Lawrence on April 17th, 2014 [ | Read more »
Bad Vamp Review
Bad Vamp Review By Jennifer Allen on April 17th, 2014 Our Rating: :: BASIC VAMPIRIC ADVENTURESUniversal App - Designed for iPhone and iPad Run or destroy the vampires in this simple, single-screen game that lacks real bite.   | Read more »

Price Scanner via MacPrices.net

Apple restocks refurbished Mac minis starting...
The Apple Store has restocked Apple Certified Refurbished Mac minis for up to $150 off the cost of new models. Apple’s one-year warranty is included with each mini, and shipping is free: - 2.5GHz Mac... Read more
Hyundai Brings Apple CarPlay To The 2015 Sona...
Hyundai Motor America has announced it will bring Apple CarPlay functionality to the 2015 Sonata. CarPlay is pitched as a smarter, safer and easier way to use iPhone in the car and gives iPhone users... Read more
Updated iPads Coming Sooner Than We Had Thoug...
MacRumors, cites KGI securities analyst Ming Chi Kuo, well-respected as an Apple product prognisticator, saying that Apple will introduce an upgraded iPad Air and iPad mini in 2014/Q3, meaning the... Read more
Toshiba Unveils New High And Low End Laptop M...
Toshiba has announced new laptop models covering both the high-end and low-end of the notebook computer spectrum. Toshiba 4K Ultra HD Laptop Toshiba’s new Satellite P55t features one of the world’s... Read more
Save up to $270 with Apple refurbished 13-inc...
The Apple Store has Apple Certified Refurbished October 2013 13″ Retina MacBook Pros available starting at $1099, with models up to $270 off MSRP. Apple’s one-year warranty is standard, and shipping... Read more
Apple now offering refurbished iPad mini with...
The Apple Store has Certified Refurbished 2nd generation iPad minis with Retina Displays now available starting at $339. Apple’s one-year warranty is included with each model, and shipping is free.... Read more
Microsoft Blinks – Drops Microsoft Office 365...
Microsoft has dropped the annual subscription fee for Microsoft Office 365 Personal – which is needed in order to create and edit documents in Microsoft Office for iPad. However, Apple’s iOS and OS X... Read more
New AVG Vault Apps for iOS and Android Help K...
AVG Technologies N.V. an online security company for 177 million active users, has announced the launch of its latest mobile application, AVG Vault. The free app introduces an innovative user... Read more
Free Local Carrot iPhone App Helps Find Fresh...
I love fresh vegetables. I’m not a vegan, although I was for several years in the 1980s, but fresh vegetables and other whole foods are still my dietary mainstays as a matter of taste rather than... Read more
CarSO Pro – Car Service and Finance Manager/O...
Lviv, Ukraine-based BM-Studios’ CarSO Pro is a tool to manage operations concerning your car. Never forget to change the oil or prolong the insurance for your car. Remember when you’ve done the car... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**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* Retail - Manager - Holyoke - Apple I...
Job Summary Keeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you’re a master of them all. In the store’s fast-paced, Read more
*Apple* Retail - Manager - Apple (United Sta...
Job SummaryKeeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you're a master of them all. In the store's fast-paced, dynamic Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**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* Retail - Market Leader - Cincinnati...
…challenges of developing individuals, building teams, and affecting growth across Apple Stores. You demonstrate successful leadership ability - focusing on excellence Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.