TweetFollow Us on Twitter

Jan 94 Challenge
Volume Number:10
Issue Number:1
Column Tag:Programmers’ Challenge

Programmers’ Challenge

Connect The Dots

By Mike Scanlin, MacTech Magazine Regular Contributing Author

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

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 (except for those challenges specifically stated to be in assembly). 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.

CONNECT THE DOTS

Thanks to James Goebel (location unknown) for suggesting this month’s challenge. You are given a set of Points and a PixMapHandle. The goal is to quickly draw a line from each point in the set to the next point in the set (if you have n points then draw n-1 line segments). A really fast version of this routine would help improve the speed of a program that makes line charts, for instance.

The prototype of the function you write is:

/* 1 */
void ConnectTheDots(numDots, theDots, 
 thePixMapHndl, lineColor)
unsigned short numDots;
Point   theDots[];
PixMapHandlethePixMapHndl;
RGBColorlineColor;

NumDots is the 1-based number of Points in the array theDots (range is 2..500). ThePixMapHandle is a handle to the PixMap where the line drawing takes place (maximum dimensions are 4000 pixels square). In order to avoid sub-byte addressing problems, you can assume that the only combinations of pixelSize, cmpSize and cmpCount of the PixMap you’ll have to deal with are (8, 8, 1), (16, 5, 3) and (32, 8, 3) (basically, 256 indexed colors, 16-bit direct (Thousands) and 32-bit direct (Millions)).

LineColor is the RGBColor that you should use to draw each line segment. If the PixMap is indexed then you’ll have to convert the RGBColor to the appropriate index value (using the inverse table of the PixMap’s pmTable field). You may assume that each point in theDots array lies within the bounds of the PixMap. And it’s okay to write or clear the unused bits of each pixel (the alpha bit(s) in the 16-bit or 32-bit direct cases).

Here’s an example: Say numDots is 4, theDots[0] = (1,2), theDots[1] = (1,4), theDots[2] = (2,4) and theDots[3] = (3,6). You would draw 3 lines of the appropriate color from (1,2) to (1,4), from (1,4) to (2,4) and from (2,4) to (3,6).

That’s it. Pretty simple concept, huh? The key is, though, that you can probably do better than the ROM’s Line or LineTo routines given the special circumstances that this drawing takes place in. Your pen size is (1,1), the mode is patCopy, there is no clipping or bounds checking, etc. It boils down to how fast your line algorithm is and how fast you can do byte-aligned pixel addressing. It is not necessary to exactly match QuickDraw’s Line routine; that is, you don’t have to plot the exact same set of pixels when making a line from a given point to some other given point. But your line routine should produce reasonable unbroken lines nonetheless.

TWO MONTHS AGO WINNER

Of the 21 entries I received for the Who Plays Who challenge I only had to disqualify 3 entries: one that used tables of precomputed answers, one that was written in Pascal and one that was incorrect. Of those remaining there were two who were equally fast: Bill Karsh (Chicago, IL) and two-time Challenge winner Bob Boonstra (Westford, MA). Bill wins, though, because his code and data size is about a quarter of Bob’s.

Here are the times, code+data sizes and outpTop 10ut sizes of each entry (the output size represents the concatenated output for many sample runs of the routine). Numbers in parens after a person’s name indicate how many times that person has finished in the top 5 places of all previous Programmer Challenges, not including this one.

Name time code+data output size

Bill Karsh (1) 4 660 27935

Bob Boonstra (3) 4 2430 29157

James Goebel (1) 7 348 29157

Doug Currie 8 298 29066

P Kidwell & G Klesczewski 8 468 29113

Dan Farmer 8 526 29157

Jerry Panagrossi 12 508 29183

Thomas Studer 12 906 29158

Martin Caron 16 676 29158

Jorj Bauer 28 11040 28936

John Chen 34 1828 29027

Michael Panchenko 73 270 35944

Dave Darah 73 780 33682

Allen Stenger (2) 74 728 35158

Stefan Pantke 76 764 33075

Steve Gehrman 81 1294 28813

Jan de Ruiter 145 354 76431

Jeremy Vineyard (1) 4561 592 29069

One thing that the two fastest entries have in common is that they don’t call fprintf (which takes up the bulk of the time for most solutions). Instead, they format the output themselves (since the format requirements are simple), buffer the output to one of their own buffers (allocated on the stack) and then call fwrite (see Bill’s solution below for an example of this).

Although I disqualified the entry from Ernst Munter (Kanata, ON, Canada) for using entirely too many precomputed lookup tables, his output format was interesting (and very compact). Here’s a sample for 12 teams:

Matches are played every 15 minutes,

starting at noon. Teams meet each other

in the designated playing areas.

Playing Areas:

A = Field 1

B = Field 2

C = Field 3

D = Field 4

E = Field 5

F = Field 6

Time: 12 . . . 1 . . . 2 . .

Team:

CycleStealers A A A A A A A A A A A

Beanies A B B B B B B B B B B

RiscTakers B A B C C C C C C C C

GiraffeButts B B A D D D D D D D D

BlueBombers C C C A B E E E E C D

Wackos C D D B A F F F F D C

Peashooters D C D E E A B C D E E

SourGrapes D D C F F B A D C F F

SnowBirds E E E C D E F A B E F

Monarchs E F F D C F E B A F E

Accountants F E F E F C D E F A B

Friends F F E F E D C F E B A

Here’s Bill’s winning solution:

/* 2 */
/* ScheduleMatches ----------------------------------------
 *
 * In response to Nov 93 MacTech programmer's challenge.
 *
 * Object is to:
 * 1)   form all combinations of 'numTeams' 'teamNames',
 * taken two at a time (numTeams even);
 * 2) match these pairs to 'numTeams'/2
 * 'playingAreaNames';
 * 3) schedule 'numTeams'/2 "matches" at a time, starting
 * at 12 noon, with a new set of such matches
 * scheduled every 15 minutes, until all combinations
 * are used;
 * 4) write the whole schedule out to a given ANSI file
 * stream.
 *
 * Some observations:
 *
 * number of combinations = C(numTeams,2) =
 * numTeams*(numTeams-1)/2.
 * There are then (numTeams-1) sets of matches, or,
 * times, which must be scheduled.
 *
 * The pairs can be generated geometrically using
 * central cyclical pattern as demonstrated for
 * numTeams = 6:
 *
 *          1           Connecting rods have fixed
 *          |           orientation.  0 stays in center.
 *          |           Other digits cycle clockwise, 
 *    2---\ 0 /---5     or, cc, around circumference.
 *         ---
 *
 *       3-----4
 *
 * Suggested formatting is as follows:
 *
 * 12:xx
 * areaU: nameJ vs nameK
 * areaV: nameL vs nameM
 * .
 * .
 * {blank line}
 * 12:xx
 * .
 * .
 *
 * billKarsh - solution author.
 *
 */

#pragma options( honor_register, !assign_registers )
#pragma options( !check_ptrs )

#include<string.h>
#include<stdio.h>

void ScheduleMatches(
 unsigned short  numTeams,
 Str255 teamNames[],
 Str255 playingAreaNames[],
 FILE   *outputfile );

#define BufSize  1024

// BufIt modifier codes
#define kTime    -1// write time
#define kStrn    1 // write string + '\n'
#define kStrSep  2 // write string + ': '
#define kStrVs   4 // write string + ' vs '

// useful shorthand inside BufIt
// make sure n bytes available in buffer,
// else empty it out

#define BufReady( n )\
 if( n > b->avail ) {\
 b->p = p;\
 BufFlush();\
 p = b->buf;\
 }

typedef struct {
 FILE   *file; // ANSI stream
 Byte   *buf;  // start of private buffer
 Byte   *p; // current position in buffer
 short  avail; // available bytes in buffer
 short  padding;// global data 4-byte aligned
} BufRec;

static  BufRec gBuf;


/* BufFlush -----------------------------------------------
 *
 * Write current buffer to file.
 */
 
static void BufFlush( void )
{
 register BufRec *b = &gBuf;
 size_t  n = b->p - b->buf;
 
 if( n ) {
 
 fwrite( b->buf, 1, n, b->file );
 
 // reset buffer
 
 b->p   = b->buf;
 b->avail = BufSize;
 }
}


/* BufIt --------------------------------------------------
 *
 * 1) Write string to local buffer if room,
 * otherwise,
 * 2) Dump buffer to file,
 * 3) resume with step 1.
 *
 * If behavior code, mod, as defined above is >= 0:
 * data is data starting address,
 * nBytes of data to write.
 *
 * If mod is special code kTime:
 * data indexes internal minute string,
 * nBytes = hour.
 */
 
static void BufIt(
 register Byte *data,
 register short  nBytes,
 short  mod )
{
 register BufRec *b= &gBuf;
 register Byte *p= b->p;
 static  Byte  mins[8]  = "00153045";

 if( mod < 0 ) { // write a time
 
 BufReady( 7 );
 
 *p++ = '\n';
 
 // hour
 
 if( !nBytes ) {
 *p++ = '1';
 *p++ = '2';
 b->avail--;
 }
 else
 *p++ = nBytes + '0';
 
 *p++  =':';
 
 // mins
 
 data += (long)mins;
 *p++ = *data++;
 *p++ = *data;
 
 *p++ = '\n';
 b->avail -= 6;
 }
 else { // write a string
 
 BufReady( nBytes + mod );
 
 memcpy( p, data, nBytes );
 p += nBytes;
 b->avail -= nBytes + mod;
 
 switch( mod ) { // write string suffix
 case kStrn:
 *p++ = '\n';
 break;
 case kStrSep:
 *p++ = ':';
 *p++ = ' ';
 break;
 case kStrVs:
 *p++ = ' ';
 *p++ = 'v';
 *p++ = 's';
 *p++ = ' ';
 break;
 }
 }
 
 b->p = p;
}


/* ScheduleMatches ----------------------------------------
 *
 * Driver routine.
 */
 
void ScheduleMatches(
 unsigned short  numTeams,
 Str255 teamNames[],
 Str255 playingAreaNames[],
 FILE   *outputfile )
{
 register Byte *area, *tmJ, *tmK;
 register short  N = numTeams,
 set  = 0, nAreas;
 register long t1= (long)*teamNames + 256,
 tN= t1 + ((N-2)<<8);
 Byte   localBuf[BufSize];
 
 if( !N || N & 1 ) return;
 
// init local buffer

 gBuf.file= outputfile;
 gBuf.buf = gBuf.p = localBuf;
 gBuf.avail = BufSize;
 
 // loop over sets of matches (times)
 
 do {
 
 // do first pair separately, because team[0]
 // is at center, so this pair disjoint from
 // others.
 
 nAreas = N>>1;
 area = *playingAreaNames;
 
 BufIt( (Byte*)((set&3)<<1), set>>2, kTime );
 BufIt( area+1, *area, kStrSep );
 
 tmJ = (Byte*)t1 - 256;
 tmK = (Byte*)t1 + (set<<8);
 
 BufIt( tmJ+1, *tmJ, kStrVs );
 BufIt( tmK+1, *tmK, kStrn  );
 
 tmJ = tmK;
 
 // loop over remaining areas (pairs)
 
 while( --nAreas ) {
 
 area += 256;
 BufIt( area+1, *area, kStrSep );
 
 // next pair
 
 tmJ = (long)tmJ < tN ? tmJ+256 : (Byte*)t1;
 tmK = (long)tmK > t1 ? tmK-256 : (Byte*)tN;
 
 BufIt( tmJ+1, *tmJ, kStrVs );
 BufIt( tmK+1, *tmK, kStrn  );
 };
 
 } while( ++set < N - 1 );
 
 BufFlush();
}
 
AAPL
$98.38
Apple Inc.
-0.64
MSFT
$43.89
Microsoft Corpora
-0.09
GOOG
$585.61
Google Inc.
-4.99

MacTech Search:
Community Search:

Software Updates via MacUpdate

Drive Genius 3.2.4 - Powerful system uti...
Drive Genius is an OS X utility designed to provide unsurpassed storage management. Featuring an easy-to-use interface, Drive Genius is packed with powerful tools such as a drive optimizer, a... Read more
Vitamin-R 2.15 - Personal productivity t...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more
Toast Titanium 12.0 - The ultimate media...
Toast Titanium goes way beyond the very basic burning in the Mac OS and iLife software, and sets the standard for burning CDs, DVDs, and now Blu-ray discs on the Mac. Create superior sounding audio... Read more
OS X Yosemite Wallpaper 1.0 - Desktop im...
OS X Yosemite Wallpaper is the gorgeous new background image for Apple's upcoming OS X 10.10 Yosemite. This wallpaper is available for all screen resolutions with a source file that measures 5,418... Read more
Acorn 4.4 - Bitmap image editor. (Demo)
Acorn is a new image editor built with one goal in mind - simplicity. Fast, easy, and fluid, Acorn provides the options you'll need without any overhead. Acorn feels right, and won't drain your bank... Read more
Bartender 1.2.20 - Organize your menu ba...
Bartender lets you organize your menu bar apps. Features: Lets you tidy your menu bar apps how you want. See your menu bar apps when you want. Hide the apps you need to run, but do not need to... Read more
TotalFinder 1.6.2 - Adds tabs, hotkeys,...
TotalFinder is a universally acclaimed navigational companion for your Mac. Enhance your Mac's Finder with features so smart and convenient, you won't believe you ever lived without them. Tab-based... Read more
Vienna 3.0.0 RC 2 :be5265e: - RSS and At...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more
VLC Media Player 2.1.5 - Popular multime...
VLC Media Player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, MP3, OGG, ...) as well as DVDs, VCDs, and various streaming protocols. It... Read more
Default Folder X 4.6.7 - Enhances Open a...
Default Folder X attaches a toolbar to the right side of the Open and Save dialogs in any OS X-native application. The toolbar gives you fast access to various folders and commands. You just click... Read more

Latest Forum Discussions

See All

Note Review
Note Review By Jennifer Allen on July 29th, 2014 Our Rating: :: TOO SIMPLEiPhone App - Designed for the iPhone, compatible with the iPad Note is a note taking app that’s a little too short on features to be worth its asking price... | Read more »
Chainsaw Warrior Goes on Sale & Ther...
Chainsaw Warrior Goes on Sale & There’s a Chance to Win a Copy of the Original Board Game Posted by Jennifer Allen on July 29th, 2014 [ permalink | Read more »
It Came From Canada: Tiny Tower Vegas
If you go to a casino, you might make a lot of money. If you run a casino, you’re guaranteed to make a lot of money. The choice seems pretty obvious. So while waiting for your shady real estate deals to move forward, get prepared with Tiny Tower... | Read more »
Z Hunter Review
Z Hunter Review By Lee Hamlet on July 29th, 2014 Our Rating: :: RIGHT ON TARGETUniversal App - Designed for iPhone and iPad While it might not necessarily break new ground, Z Hunter has enough tricks up its sleeve to ensure that... | Read more »
Huge Update Comes To Duet, Adding 48 New...
Huge Update Comes To Duet, Adding 48 New Stages Posted by Jennifer Allen on July 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Sharknado: The Video Game Available Now....
Sharknado: The Video Game Available Now. Seriously. Posted by Rob Rich on July 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Frog Orbs 2 Review
Frog Orbs 2 Review By Nadia Oxford on July 29th, 2014 Our Rating: :: THIS MAGIC IS A TAD MONOTONOUS Universal App - Designed for iPhone and iPad Frog Orbs 2 is repetitive, but younger players should enjoy it nonetheless.   | Read more »
Puzzix Review
Puzzix Review By Jennifer Allen on July 29th, 2014 Our Rating: :: NICE IDEAUniversal App - Designed for iPhone and iPad A little like Tetris, Puzzix is all about piecing together blocks and watching them vanish. It could do with... | Read more »
Cannonball eMail is Now Live – Works Wit...
Cannonball eMail is Now Live – Works With Gmail, Yahoo, Outlook, Hotmail, and AOL Posted by Jessica Fisher on July 29th, 2014 [ permalink ] | Read more »
To The End Review
To The End Review By Lee Hamlet on July 29th, 2014 Our Rating: :: A VICIOUS CYCLEUniversal App - Designed for iPhone and iPad To The End will test players’ patience, timing, and dedication as they try to navigate all 13 levels in... | Read more »

Price Scanner via MacPrices.net

The lowest prices on leftover Retina MacBook...
Best Buy has dropped prices on leftover 13″ and 15″ Retina MacBook Pros by up to $300 off original MSRP on their online store for a limited time. Choose free local store pickup (if available) or free... Read more
Apple Updates MacBook Pro with Retina Display...
Apple today updated its MacBook Pro with Retina display with faster processors and double the amount of memory in both entry-level configurations. MacBook Pro with Retina display features a Retina... Read more
Up to $250 price drop on leftover 15-inch Mac...
B&H Photo has dropped prices on 2013 15″ Retina MacBook Pros by as much as $250 off original MSRP. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.3GHz Retina MacBook Pro: $2349... Read more
Updated MacBook Pro Price Trackers
We’ve updated our MacBook Pro Price Trackers with the latest information on prices, bundles, and availability on the new 2014 models from Apple’s authorized internet/catalog resellers as well as... Read more
Apple updates MacBook Pros with slightly fast...
Apple updated 13″ and 15″ Retina MacBook Pros today with slightly faster Haswell processors. 13″ models now ship with 8GB of RAM standard, while 15″ MacBook Pros ship with 16GB across the board. Most... Read more
Apple drops price on 13″ 2.5GHz MacBook Pro b...
The Apple Store has dropped their price for the 13″ 2.5GHz MacBook Pro by $100 to $1099 including free shipping. Read more
Apple drops prices on refurbished 2013 MacBoo...
The Apple Store has dropped prices on Apple Certified Refurbished 13″ and 15″ 2013 MacBook Pros, with model now available starting at $929. Apple’s one-year warranty is standard, and shipping is free... Read more
iOS 8 and OS X 10.10 To Support DuckDuckGo As...
Writing for Quartz, Dan Frommer reports that Apple’s forthcoming iOS 8 and OS X 10.10 operating systems version updates will allow users to select DuckDuckGo as their default search engine. He notes... Read more
U.K. Hospital Using iPods and iPads To Record...
British news journal GazetteLive’s. Ian McNeal notes that the old “an apple a day keeps the doctor away” proverb is being turned on its head at http://southtees.nhs.uk/hospitals/james-cook/ James... Read more
13-inch 2.5GHz MacBook Pro on sale for $1099,...
Best Buy has the 13″ 2.5GHz MacBook Pro available for $1099.99 on their online store. Choose free shipping or free instant local store pickup (if available). Their price is $100 off MSRP. Price is... Read more

Jobs Board

Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full 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
Sr. Product Leader, *Apple* Store Apps - Ap...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring 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* 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
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.