TweetFollow Us on Twitter

Feb 93 Challenge
Volume Number:9
Issue Number:2
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.

Surely one of the most interesting things about life is that it’s unpredictable. You’re never quite sure exactly what is going to happen next. Think about the possibilities: Without any warning whatsoever you could meet someone you haven’t seen for years, a meteor could slam into the side of your house, Elvis could reappear, or the MacTech Magazaine Programmers’ Challenge deadline could be moved up after it had been published. Just knowing that these types of things could happen certainly does keep one on one’s toes, no?

Surprise! Due to gremlins in the production room, the deadline for the Nov/Dec puzzle was stated as being Jan 1st instead of the correct date of Dec 1st. Our apologies. To be fair, we will honor all submissions received up until Jan 1st and if a better one than the winner given below comes in we will publish the new winner next month. Hopefully the gremlin traps we’ve set will prevent this from happening again. Or, since this is the second time this has happened, maybe this month’s Challenge should be to accurately guess its deadline date...

The if-nothing-better-comes-in-before-Jan-1st winner of the “Millions of Colors?” challenge is Tom Pinkerton (Wilmette, IL). While I applaud his use of a minimal initialization loop and hard-coded array indexes, there is one thing that could be improved. This loop:

 register long*  sInitPtr;
 register long i;

 sInitPtr = sBluListPtr;
 i = 64;
 while (i--) {
 sInitPtr[3] =
 sInitPtr[2] =
 sInitPtr[1] =
 sInitPtr[0] = -1;
 sInitPtr += 4;
 }

could be better written as:

 register long*  sInitPtr;
 register long i, minusOne;

 sInitPtr = sBluListPtr;
 minusOne = -1;
 i = 64*4;
 do {
 *sInitPtr++ = minusOne;
 } while (--i);

which executes faster and is fewer bytes. Other than that little nit, Tom’s solution is clever and well implemented.

New E-Mail Addresses!

In the quest for better ways to work the Programmers’ Challenge, we have added a series of e-mail addresses for the puzzle. Please use these addresses. AppleLink: MT.PROGCHAL, Internet: progchallenge@xplain.com, and CompuServe: 71552,174.

Remember, that you cannot send files over Internet, but you can just send a message with the code in the message.

Insane Anglo Warlord

Did anyone see Sneakers? The movie itself had extremely few redeeming qualities but there was an interesting effect that they did with the credits. The movie was about secret codes. Each person’s name that came up had the letters scrambled to make valid English words which would then descramble themselves to be the person’s name (without adding or deleting any letters). For instance, Robert Redford initially came up as Fort Red Border and then descrambled to Robert Redford through a series of letter rearrangement steps.

What I’d like to do is ask you to write the routine that would come up with Fort Red Border (or any other valid set of English words) when given Robert Redford as input. But that would require the use of a large word list that I’m almost positive Neil wouldn’t want to print in this tiny little column. So, instead, I’m going to ask for a subset of this effect. Given the starting string, the ending string and the desired number of steps, the challenge is to come up with the intermediate strings in an appropriately interesting way (which may or may not involve some randomness-your decision).

The prototype of the function you write is:

void Descramble(startString, endString, numSteps, 
 stepStringPtrs)
Str255  startString, endString;
unsigned short   numSteps;
Str255  *stepStringPtrs[20];

Example:

 Input:
 startString = “\pFORT RED BORDER”
 endString = “\pROBERT REDFORD ” <note space at end>
 numSteps = 4
 stepStringPtrs = <numSteps pointers to Str255s allocated
 by the caller>

 Output:
 *stepStringPtrs[0] = “\pROOR TED BFRDER”
 *stepStringPtrs[1] = “\pRORRET D BFODER”
 *stepStringPtrs[2] = “\pROBDET R RFORED”
 *stepStringPtrs[3] = “\pROBEDT RERFORD ”

You can assume the input and output strings each have the same number of uppercase letters, which is at least twice numSteps (i.e. the minimum string length for a 4 step puzzle is 8 characters). Each intermediate string should match the final string a little bit better than the previous one (in terms of the number of letters that are in their final correct positions). There is no “correct” algorithm here-it’s up to you to devise one (i.e. your solution does not need to exactly match the example output given here). Unlike previous Programmer Challenges, this one will be judged primarily on effect, not speed. I’m looking for a smooth transition from startString to endString (and if it’s really fast and small then that’s an extra bonus).

So, who can guess what you get if you rearrange the letters in “Ronald Wilson Reagan”?

Here is Tom’s winning solution to the Nov/Dec Challenge:

// UniqueRGBValues.c:
//   A function that returns the number of
//   unique colors found in a 24-bit RGB image.
// Author: Tom Pinkerton

unsigned long
UniqueRGBValues(Ptr baseAddress,
 short numRows, short numCols)
{
 Handle sBuffers = nil;
 long   sUniquePixels = 0;

// Allocate memory for the data
// structures. We will need:
// 256 x 4 bytes for the unique blue value table.
// 256 x 256 x 8 bytes for the Red/Green
//   intersection grid.
// numRows x numCols x 4 bytes for the
//   master blue list.
 sBuffers = NewHandle((((long)numRows *
  (long)numCols) * 4L) + 525312);
 if (sBuffers != nil) {
 
 // Setup pointers to the data structures.
 long*  sBluListPtr =
  (long*)((char*)*sBuffers + 0);
 long*  sRGTablePtr =
  (long*)((char*)*sBuffers + 1024);
 long*  sRGLinksPtr =
  (long*)((char*)*sBuffers + 525312);
 long*  sRGBase = nil;
 
// Initialize the Red/Green intersection
// grid and the master Blue list with 
// -1's.
 {
 register long*  sInitPtr;
 register long i;
 
// A -1 in this table means that the blue
// value for a particular Red/Green
// combination is not yet found.
 sInitPtr = sBluListPtr;
 i = 64;
 while (i--) {
 sInitPtr[3] =
 sInitPtr[2] =
 sInitPtr[1] =
 sInitPtr[0] = -1;
 sInitPtr += 4;
 }
 
// Only the blue list link need be
// initialized (first of two longs) for
// each element. A -1 means that a unique
// Red/Green pair represented by this
// intersection has not yet been found.
 sInitPtr = sRGTablePtr;
 i = 4096;
 while (i--) {
 sInitPtr[30] =
 sInitPtr[28] =
 sInitPtr[26] =
 sInitPtr[24] =
 sInitPtr[22] =
 sInitPtr[20] =
 sInitPtr[18] =
 sInitPtr[16] =
 sInitPtr[14] =
 sInitPtr[12] =
 sInitPtr[10] =
 sInitPtr[ 8] =
 sInitPtr[ 6] =
 sInitPtr[ 4] =
 sInitPtr[ 2] =
 sInitPtr[ 0] = -1;
 sInitPtr += 32;
 }
 }
 
// Scan the image to create a linked list of blue values at 
// each unique Red/Green intersection. Each element in the
// Red/Green intersection grid consists of the first link 
// of that intersection's blue list (initially -1) and a 
// link to the next Red/Green intersection which contains 
// a blue list. Whereas the Red/Green link is a pointer 
// to the next Red/Green intersection, a blue list link 
// holds an array index in its low order 3 bytes and an 
// actual blue value in its high order byte. The blue link
// index refers to an element in the master blue list. 
// Each master blue list element then points to the next 
// blue value link within a specific blue list or terminates 
// the list with a -1 value.
 {
 register unsigned char*
 sPixelsPtr = (unsigned char*)baseAddress;
 register long* sRGPtr;
 register long*  sLinkPtr = sRGLinksPtr;
 register long sLinkIndex = 0;
 register long sNumPixels = 
 (long)numRows * (long)numCols;
 
// For each pixel in the image, do the following.
 while (sNumPixels--) {
 
// Concatenate the red and green values to create an offset 
// used to point at the unique Red/Green element in the
// Red/Green intersection grid.
 sRGPtr = sRGTablePtr +
  ((((long)sPixelsPtr[1] << 8) |
  (long)sPixelsPtr[2]) << 1);
 
// If this is the first pixel with this particular Red/Green 
// combination, then add the Red/Green intersection to the
// Red/Green linked list.
 if (sRGPtr[0] == -1) {
 sRGPtr[1] = (long)sRGBase;
 sRGBase = sRGPtr;
 }
 
// Create a new blue link with the pixel's blue value and 
// add it to Red/Green intersection's blue list.
 *sLinkPtr = sRGPtr[0];
 sRGPtr[0] = sLinkIndex | ((long)sPixelsPtr[3] << 24);
 
// Increment stuff for the next go 'round.
 ++sLinkPtr;
 ++sLinkIndex;
 sPixelsPtr += 4;
 }
 }
 
// For each list of blue values at a unique Red/Green 
// intersection,  determine the number of unique blue
// values in that list. This calculates the number of unique 
// colors that have the same Red and Green values.
// Accumulating the number of unique colors at every 
// Red/Green intersection gives us the total 
// number of unique colors.
 {
 register long*  sRGPtr = sRGBase;
 register long*  sBlueBase = nil;
 register long*  sBluePtr;
 register long   sLinkIndex;
 
// For each Red/Green intersection found above, do the 
// following.
 while (sRGPtr != nil) {
 
// Walk the list of blue values for this Red/Green pair. 
// For each one, do the following.
 sLinkIndex = sRGPtr[0];
 while (sLinkIndex != -1) {
 
// Create a pointer to the unique blue value element.
 sBluePtr = sBluListPtr +
 ((unsigned long)sLinkIndex >> 24);
 
// A -1 here means that the unique R/G and B color has not 
// yet been counted.  Therefore, mark the fact that it has
// been counted by adding the element to a linked list 
// and incrementing the unique color count. The blue value 
// linked list is used later to quickly reset itself.
 if (*sBluePtr == -1) {
 *sBluePtr = (long)sBlueBase;
 sBlueBase = sBluePtr;
 ++sUniquePixels;
 }
 
// Get the next blue list link in the blue list.
 sLinkIndex = sRGLinksPtr[sLinkIndex & 0x00FFFFFF];
 }
 
// Reset the blue count list by walking its links and 
// replacing them again with -1's.
 sBluePtr = sBlueBase;
 while (sBluePtr != nil) {
 sBlueBase = (long*)*sBluePtr;
 *sBluePtr = -1;
 sBluePtr = sBlueBase;
 }
 sBlueBase = nil;
 
// Get next Red/Green intersection.
 sRGPtr = (long*)sRGPtr[1];
 }
 }
 
 DisposHandle(sBuffers);
 }
 return(sUniquePixels);
}

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. 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

Tweetbot 2.5.3 - Popular Twitter client.
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Hopper Disassembler 4.2.19- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
Monosnap 3.4.0 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with our... Read more
Duet 1.6.5.5 - Use your iPad as an exter...
Duet is the first app that allows you to use your iDevice as an extra display for your Mac using the Lightning or 30-pin cable. Note: This app requires a $14.99 iOS companion app. Version 1.6.5.5:... Read more
Hopper Disassembler 4.2.19- - Binary dis...
Hopper Disassembler is a binary disassembler, decompiler, and debugger for 32- and 64-bit executables. It will let you disassemble any binary you want, and provide you all the information about its... Read more
Duet 1.6.5.5 - Use your iPad as an exter...
Duet is the first app that allows you to use your iDevice as an extra display for your Mac using the Lightning or 30-pin cable. Note: This app requires a $14.99 iOS companion app. Version 1.6.5.5:... Read more
Monosnap 3.4.0 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with our... Read more
Tweetbot 2.5.3 - Popular Twitter client.
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Default Folder X 5.1.6 - 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 on... Read more
Evernote 6.12.3 - Create searchable note...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more

The best new games we played this week -...
It's pretty much been one big release after another. We were privy to a bunch of surprises this week, with a lot of games we'd been waiting for quite some time dropping unexpectedly. We hope you're free this weekend, because there is a lot for... | Read more »
Stormbound: Kingdom Wars guide - how to...
Stormbound: Kingdom Wars is an excellent new RTS turned card battler out now on iOS and Android. Lovers of strategy will get a lot of enjoyment out of Stormbound's chess-like mechanics, and it's cardbased units are perfect for anyone who loves the... | Read more »
The best AR apps and games on iOS right...
iOS 11 has officially launched, and with it comes Apple's ARKit, a helpful framework that makes it easier than ever for developers to create mobile AR experiences. To celebrate the occassion, we're featuring some of the best AR apps and games on... | Read more »
Phoenix Wright: Ace Attorney - Spirit of...
Phoenix Wright: Ace Attorney - Spirit of Justice 1.00.00 Device: iOS Universal Category: Games Price: $.99, Version: 1.00.00 (iTunes) Description: ************************************************※IMPORTANT※・Please read the “When... | Read more »
Kpressor (Utilities)
Kpressor 1.0.0 Device: iOS Universal Category: Utilities Price: $4.99, Version: 1.0.0 (iTunes) Description: The ultimate ZIP compression application for iPhone and iPad. - Full integration of iOS 11 with support for multitasking.-... | Read more »
Find out how you can save £35 and win a...
Nothing raises excitement like a good competition, and we’re thrilled to announce our latest contest. We’ll be sending one lucky reader and a friend to the Summoners War World Arena Championship at Le Comedia in Paris on October 7th. It’s the... | Read more »
Another Lost Phone: Laura's Story...
Another Lost Phone: Laura's Story 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Another Lost Phone is a game about exploring the social life of a young woman whose phone you have just... | Read more »
The Witness (Games)
The Witness 1.0 Device: iOS Universal Category: Games Price: $9.99, Version: 1.0 (iTunes) Description: You wake up, alone, on a strange island full of puzzles that will challenge and surprise you. You don't remember who you are, and... | Read more »
Egg, Inc. guide - how to build your gold...
Egg, Inc.'s been around for some time now, but don't you believe for one second that this quirky clicker game has gone out of style. The game keeps popping up on Reddit and other community forums thanks to the outlandish gameplay (plus, the... | Read more »
The best deals on the App Store this wee...
Good news, everyone! Your favorite day of the week has arrived at last -- it's discount roundup day! This fine Wednesday evening we're gathering up the hottest deals on the App Store. We've got action platformers, we've got puzzle games, we've got... | Read more »

Price Scanner via MacPrices.net

Looking for a 2017 12″ Retina MacBook? Save $...
Apple has Certified Refurbished 2017 12″ Retina MacBooks available for $200-$240 off the cost of new models. Apple will include a standard one-year warranty with each MacBook, and shipping is free.... Read more
Apple Offering Up To $455 Credit Toward iPhon...
iPhone 8 and 8 Plus are now available at the Apple Store, and you can receive up to $375 credit toward a new iPhone purchase when you trade in your eligible smartphone. Photo Courtesy Apple Just... Read more
AnyTrans Offers iOS Users Three Ways For Movi...
iMobie Inc. today announceed AnyTrans v6.0.1, which now can help iOS users move all data to iPhone 8/8 Plus seamlessly. The software is available both on Mac and Windows and fully able to move all... Read more
Snag a 13-inch 2.3GHz MacBook Pro for $100 of...
B&H Photo has 2017 13″ 2.3GHz MacBook Pros in stock today and on sale for $100 off MSRP, each including free shipping plus NY & NJ sales tax only: – 13-inch 2.3GHz/128GB Space Gray MacBook... Read more
Verizon offers new iPhone 8 for $100-$300 off...
Verizon is offering the new iPhone 8 for up to $300 off MSRP with an eligible trade-in: • $300 off: iPhone 6S/6S Plus/7/7 Plus, Google Pixel XL, LG G6, Moto Z2 Force, Samsung Galaxy S7/S7 edge/S8/S8... Read more
Apple Refurbished 2017 13-inch MacBook Pros a...
Apple has Certified Refurbished 2017 13″ Touch Bar MacBook Pros in stock today and available for $200-$300 off MSRP. A standard Apple one-year warranty is included with each MacBook, and shipping is... Read more
OWC USB-C Travel Dock with 5 Ports Connectivi...
OWC have announced the new OWC USB-C Travel Dock, the latest addition to their line of connectivity solutions. The USB-C Travel Dock lets you connect its integrated USB-C cable to a Mac or PC laptop... Read more
Pelican Products, Inc. Unveils Cases For All...
Pelican Products, Inc. has announced the launch of its full line of cases including Voyager, Adventurer, Protector, Ambassador, Interceptor (for the Apple iPhone 8 and 8 Plus backwards compatible... Read more
$100 off new 2017 13-inch MacBook Airs
B&H Photo has 2017 13″ MacBook Airs on sale today for $100 off MSRP including free shipping. B&H charges NY & NJ sales tax only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off... Read more
Apple restocks Certified Refurbished 13-inch...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $719 and 2016 models available starting at $809. An Apple one-year warranty is included with each MacBook, and shipping is... Read more

Jobs Board

Instructional Designer, *Apple* Product Doc...
Job Summary The Apple Product Documentation team is looking for an instructional designer or a video editor to write user documentation for its professional video Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Development Operations and Site Reliability E...
Development Operations and Site Reliability Engineer, Apple Payment Gateway Job Number: 57572631 Santa Clara Valley, California, United States Posted: Jul. 27, 2017 Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with Tennessee Interviews but with Apple , Inc. Tennessee Interviews is a private organization that works in collaboration with Read more
Specialist - Retail Customer Services and Sal...
The position listed below is not with South Carolina Interviews but with Apple , Inc. South Carolina Interviews is a private organization that works in collaboration Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.