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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

LibreOffice 4.4.5.2 - 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
Adobe Lightroom 6.1.1 - Import, develop,...
Adobe Lightroom is available as part of Adobe Creative Cloud for as little as $9.99/month bundled with Photoshop CC as part of the photography package. Lightroom 6 is also available for purchase as a... Read more
File Juicer 4.41 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. It finds and... Read more
A Better Finder Rename 9.52 - 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
OmniFocus 2.2.3 - GTD task manager with...
OmniFocus helps you manage your tasks the way that you want, freeing you to focus your attention on the things that matter to you most. Capturing tasks and ideas is always a keyboard shortcut away in... Read more
TinkerTool 5.4 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Tinderbox 6.3.1 - Store and organize you...
Tinderbox is a personal content management assistant. It stores your notes, ideas, and plans. It can help you organize and understand them. And Tinderbox helps you share ideas through Web journals... Read more
Parallels Desktop 10.2.2 - Run Windows a...
Parallels Desktop is simply the world's bestselling, top-rated, and most trusted solution for running Windows applications on your Mac. With Parallels Desktop for Mac, you can seamlessly run both... Read more
Adobe Premiere Pro CC 2015 9.0.1 - Digit...
Premiere Pro CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous Premiere Pro customer). Premiere Pro CS6 is still available for... Read more
Adobe After Effects CC 2015 13.5.1 - Cre...
After Effects CC 2015 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous After Effects customer). After Effects CS6 is still available... Read more

Domino Drop (Games)
Domino Drop 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Domino Drop is a delightful new puzzle game with dominos and gravity!Learn how to play it in a minute, master it day by day.Your... | Read more »
OPERATION DRACULA (Games)
OPERATION DRACULA 1.0.1 Device: iOS Universal Category: Games Price: $5.99, Version: 1.0.1 (iTunes) Description: 25% off launch sale!!! 'Could prove to be one of the most accurate representations of the Japanese bullet hell shmup... | Read more »
Race The Sun (Games)
Race The Sun 1.01 Device: iOS iPhone Category: Games Price: $4.99, Version: 1.01 (iTunes) Description: You are a solar craft. The sun is your death timer. Hurtle towards the sunset at breakneck speed in a futile race against time.... | Read more »
Tap Delay (Music)
Tap Delay 1.0.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0.0 (iTunes) Description: Back in the “old days”, producers and engineers created delay and echo effects using tape machines. Tap Delay combines the warm... | Read more »
This Week at 148Apps: July 20-24, 2015
July is Heating Up With 148Apps How do you know what apps are worth your time and money? Just look to the review team at 148Apps. We sort through the chaos and find the apps you're looking for. The ones we love become Editor’s Choice, standing out... | Read more »
Red Game Without A Great Name (Games)
Red Game Without A Great Name 1.0.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.3 (iTunes) Description: The mechanical bird is flying through an unfriendly, Steampunk world. Help it avoid obstacles and deadly... | Read more »
Warhammer: Arcane Magic (Games)
Warhammer: Arcane Magic 1.0.2 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0.2 (iTunes) Description: Engage in epic battles and tactical gameplay that challenge both novice and veteran in Warhammer: Arcane Magic, a... | Read more »
Mazes of Karradash (Games)
Mazes of Karradash 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The city of Karradash is under attack: the monsters of the Shadow Realms are emerging from the depths.No adventurer is... | Read more »
Battle Golf is the Newest Game from the...
Wrassling was a pretty weird - and equally great - little wressling game. Now the developers, Folmer Kelly and Colin Lane, have turned their attention to a different sport: golfing. This is gonna be weird. [Read more] | Read more »
Qbert Rebooted has the App Store Going...
The weird little orange... whatever... is back, mostly thanks to that movie which shall remain nameless (you know the one). But anyway it's been "rebooted" and now you can play the fancy-looking Qbert Rebooted on iOS devices. [Read more] | Read more »

Price Scanner via MacPrices.net

12-inch MacBooks in stock for $20 off, save o...
Adorama has 12″ Retina MacBooks in stock for $20 off MSRP including free shipping plus NY & NJ sales tax only. For a limited time, Adorama will include a free Apple USB-C to USB Adapter, free 4-... Read more
College Student Deals: Additional $100 off Ma...
Take an additional $100 off all MacBooks and iMacs at Best Buy Online with their College Students Deals Savings, valid through August 8, 2015. Anyone with a valid .EDU email address can take... Read more
2015 13-inch 2.7GHz Retina MacBook Pro on sal...
B&H Photo has the new 2015 13″ 2.7GHz/128GB Retina MacBook Pro on sale today for $1199 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
2.8GHz Mac mini available for $988, includes...
Adorama has the 2.8GHz Mac mini available for $988, $11 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... Read more
Updated Mac Price Trackers
We’ve updated our Mac Price Trackers with the latest information on prices, bundles, and availability on systems from Apple’s authorized internet/catalog resellers: - 15″ MacBook Pros - 13″ MacBook... Read more
High-Precision Battery Fuel Gauge IC Extends...
Renesas Electronics Corporation has announced its new lithium-ion (Li-ion) battery fuel gauge IC, the RAJ240500, designed to extend battery life for connected mobile devices such as tablets, notebook... Read more
27-inch 3.3GHz 5K iMac on sale for $1799, $20...
B&H Photo has the 27″ 3.3GHz 5K iMac on sale for $1799 including free shipping plus NY tax only. Their price is $200 off MSRP, and it’s the lowest price available for this model from any Apple... Read more
Twelve South Free Dual Screen Backgrounds Co...
Twelve South has posted a second collection of travel Desktop photos, noting: For the Twelve South team, a vacation is never just a vacation. It’s a time to try out new prototypes on the road, visit... Read more
Apple Refurbished iMacs available for up to $...
The Apple Store has Apple Certified Refurbished iMacs available for up to $380 off the cost of new models. Apple’s one-year warranty is standard, and shipping is free: - 27″ 3.5GHz 5K iMac – $1949 $... Read more
Tablets: Why Microsoft’s Surface Is Soaring W...
In contrast to Apple’s record fiscal third quarter reported this week, Microsoft had a miserable latest quarter with its revenues falling by 5.1 percent, hammered by ongoing weak PC demand, and... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
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* Retail - Multiple Positions (US) - A...
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* Retail - Multiple Positions (US) - A...
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* Customer Experience (ACE) Leader - A...
…management to deliver on business objectives Training partner store staff on Apple products, services, and merchandising guidelines Coaching partner store staff on Read more
Project Manager - *Apple* Pay Security - Ap...
**Job Summary** The Apple Pay Security team is seeking a highly organized, results-driven Project Manager to drive the development of Apple Pay Security. If you are Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.