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

Tunnelblick 3.6.7beta02 - GUI for OpenVP...
Tunnelblick is a free, open source graphic user interface for OpenVPN on OS X. It provides easy control of OpenVPN client and/or server connections. It comes as a ready-to-use application with all... Read more
calibre 2.65.1 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
jAlbum Pro 13.4 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. You can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly... Read more
jAlbum 13.4 - 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
Parallels Desktop 12.0.0 - Run Windows a...
Parallels allows you to run Windows and Mac applications side by side. Choose your view to make Windows invisible while still using its applications, or keep the familiar Windows background and... Read more
Firefox 48.0.2 - Fast, safe Web browser.
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more
Apple iOS 9.3.5 - The latest version of...
iOS is the world’s most advanced mobile operating system, and it’s the foundation of iPhone, iPad, and iPod touch. It comes with a collection of apps and features that let you do the everyday things... Read more
Spotify 1.0.36.124. - Stream music, crea...
Spotify is a streaming music service that gives you on-demand access to millions of songs. Whether you like driving rock, silky R&B, or grandiose classical music, Spotify's massive catalogue puts... Read more
Apple iOS 9.3.5 - The latest version of...
iOS is the world’s most advanced mobile operating system, and it’s the foundation of iPhone, iPad, and iPod touch. It comes with a collection of apps and features that let you do the everyday things... Read more
Parallels Desktop 12.0.0 - Run Windows a...
Parallels allows you to run Windows and Mac applications side by side. Choose your view to make Windows invisible while still using its applications, or keep the familiar Windows background and... Read more

Cartoon Network Superstar Soccer: Goal!!...
Cartoon Network Superstar Soccer: Goal!!! – Multiplayer Sports Game Starring Your Favorite Characters 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Become a soccer superstar with your... | Read more »
NFL Huddle: What's new in Topps NFL...
Can you smell that? It's the scent of pigskin in the air, which either means that cliches be damned, pigs are flying in your neck of the woods, or the new NFL season is right around the corner. [Read more] | Read more »
FarmVille: Tropic Escape tips, tricks, a...
Maybe farming is passé in mobile games now. Ah, but farming -- and doing a lot of a other things too -- in an island paradise might be a little different. At least you can work on your tan and sip some pina coladas while tending to your crops. [... | Read more »
Become the King of Avalon in FunPlus’ la...
King Arthur is dead. Considering the legend dates back to the 5th century, it would be surprising if he wasn’t. But in the context of real-time MMO game King of Avalon: Dragon Warfare, Arthur’s death plunges the kingdom into chaos. Evil sorceress... | Read more »
Nightgate (Games)
Nightgate 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: *** Launch Sale: 25% OFF for a limited time! *** In the year 2398, after a great war, a network of intelligent computers known as... | Read more »
3 best fantasy football apps to get you...
Last season didn't go the way you wanted it to in fantasy football. You were super happy following your drafts or auctions, convinced you had outsmarted everyone. You were all set to hustle on the waiver wire, work out some sweet trades, and make... | Read more »
Pokemon GO update: Take me to your leade...
The Team Leaders in Pokemon GO have had it pretty easy up until now. They show up when players reach level 5, make their cases for joining their respective teams, and that's pretty much it. Light work, as Floyd Mayweather might say. [Read more] | Read more »
Ruismaker FM (Music)
Ruismaker FM 1.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0 (iTunes) Description: Following up on the success of Ruismaker, here's her crazy twin-sister, designed for people who want to design their own... | Read more »
Space Marshals 2 (Games)
Space Marshals 2 1.0.15 Device: iOS iPhone Category: Games Price: $5.99, Version: 1.0.15 (iTunes) Description: The sci-fi wild west adventure in outer space continues with Space Marshals 2. This tactical top-down shooter puts you in... | Read more »
Dungeon Warfare (Games)
Dungeon Warfare 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: Dungeon Warfare is a challenging tower defense game where you become a dungeon lord to defend your dungeon against greedy... | Read more »

Price Scanner via MacPrices.net

Clearance 12-inch Retina MacBooks, Apple refu...
Apple has Certified Refurbished 2015 12″ Retina MacBooks available starting at $929. Apple will include a standard one-year warranty with each MacBook, and shipping is free. The following... Read more
BookBook Releases SurfacePad, BookBook &...
BookBook has released three new covers just for iPad Pro: SurfacePad, BookBook and BookBook Rutledge Edition. BookBook for iPad Pro is a gorgeous leather case reminiscent of a vintage sketchbook.... Read more
Clean Text 1.0 for iOS Reduces Text Cleanup a...
Apimac today announced availability of Clean Text for iOS, a tool for webmasters, graphic designers, developers and magazine editors to reduce text cleanup and editing time, and also for any iPhone... Read more
27-inch iMacs on sale for up to $220 off MSRP
B&H Photo has 27″ Apple iMacs on sale for up to $200 off MSRP including free shipping plus NY sales tax only: - 27″ 3.3GHz iMac 5K: $2099 $200 off MSRP - 27″ 3.2GHz/1TB Fusion iMac 5K: $1899 $100... Read more
Apple refurbished 13-inch MacBook Airs availa...
Apple has Certified Refurbished 2016 and 2015 13″ MacBook Airs now available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2016 13″ 1.6GHz/8GB/... Read more
Apple refurbished iPad mini 2s available for...
Apple is offering Certified Refurbished iPad mini 2s for up to $80 off the cost of new minis. An Apple one-year warranty is included with each model, and shipping is free: - 16GB iPad mini 2 WiFi: $... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more
Mac Pros on sale for $200 off MSRP
B&H Photo has Mac Pros on sale for $200 off MSRP. Shipping is free, and B&H charges sales tax in NY only: - 3.7GHz 4-core Mac Pro: $2799, $200 off MSRP - 3.5GHz 6-core Mac Pro: $3799, $200... Read more
Will We See A 10.5″ iPad Pro in 2017? – The ‘...
A MacRumors report, cites a research note from KGI Securities analyst Ming-Chi Kuo, saying a new size iPad model is in the works. According to the highly respected Cho, who has a strong track record... Read more
IOGEAR USB-C Docking Station Transforms Lapto...
IOGEAR has announced the launch of its innovative USB-C Docking Station with Power Delivery which turns USB-C enabled laptops into desktop workstations. The new IOGEAR USB-C Docking Station features... Read more

Jobs Board

*Apple* Engineer - Softthink Solutions, Inc....
Job Description:- Proven experience in administering IOS and OSX Apple devices in enterprises - Experience in administering Apple devices in Windows environments Read more
*Apple* Professional Learning Specialist - A...
# Apple Professional Learning Specialist Job Number: 51234243 Portland, Maine, Maine, United States Posted: Aug. 18, 2016 Weekly Hours: 40.00 **Job Summary** The Read more
*Apple* Mobile Master - Best Buy (United Sta...
What does a Best Buy Apple Mobile Master do? At Best Buy, our mission is to leverage the unique talents and passions of our employees to inspire, delight, and enrich Read more
*Apple* Retail - Multiple Positions Akron, O...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Simply Mac *Apple* Specialist- Repair Techn...
…The Technician is a master at working with our customers to diagnose and repair Apple devices in a manner that exceeds the expectations set forth by Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.