TweetFollow Us on Twitter

Apr 93 Challenge
Volume Number:9
Issue Number:4
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.

Rotated Bits

This month’s challenge is to write a routine that quickly rotates a 1-bit deep bitMap 90 degrees clockwise. You are given pointers to a source bitMap and destination bitMap. Space for the destination pixels has already been allocated (the baseAddr field is valid) and the rowBytes and bounds fields have been set up for you. All you have to do is rotate the bits.

The function prototype you write is:

void RotateBitMapClockwise(srcBitMapPtr, dstBitMapPtr)
BitMap  *srcBitMapPtr;
BitMap  *dstBitMapPtr;

To check for correctness, you might want to write a test program that rotates the same bitMap four times and then diffs the result with the original (they should be identical). Have fun.

February Winner

The winner of the “Insane Anglo Warlord” challenge is Jeremy Vineyard (Lawrence, KS) whose solution was the only one of the two I received which gave valid results (the other one gave intermediate strings that had a character not in the original strings). Remember kids: you have to play the game to have a chance at winning.

Here’s the output of Jeremy’s Descramble routine when the input strings are “INSANE ANGLO WARLORD” and “RONALD WILSON REAGAN” when the number of intermediate steps is set to 10:

INSANE ANGLO WARLORD
OIDSLNE N NGWRALORAA
 ORDLINE AWNSNLORAAG
R AODSILEWANN ORALGN
R WADOSGLNIAA RLOENN
R IWODNSALRAAL OEGNN
ROD INLASL RAWOEAGNN
RONDIL A SLORWAEAGNN
RONLDLI S AORWAEAGNN
RONDL LWASIOR AEAGNN
RONWLD AILSOR AEAGNN
RONALD WILSON REAGAN

And here is Jeremy’s code to generate those strings:

/***********************************
 * Descramble.c
 * A procedure that returns a smooth 
 * transition from one string to 
 * another with the same characters, 
 * but in a different order.
 ***********************************/

#include <stdlib.h>
#include <string.h>

void Descramble(
 Str255 startString,
 Str255 endString,
 unsigned short  numSteps,
 Str255 *stepStringPtrs[20] )
{
 short  i, j, k;
 short  strLength = startString[0];
 div_t  divResult;
 short  destination, memSwitch;
 BooleanswitchPossible;

 short  distances[256];
 short  destMap[256];
 BooleandestSwitchMap[256];
 BooleancheckList[256];
 
 /* Clear the destination switching 
  * map for use. Only clear it up to 
  * strLength to save time. */
 for (i = 1; i <= strLength; i++)
 destSwitchMap[i] = false;
 
 /* This loop searches for a duplicate 
  * char 'j' for the char 'i'. Once it  * finds a duplicate, it checks 
to 
  * see whether it is already being 
  * used as another char's 
  * destination. If not, it shows that 
  * char 'j' is char 'i's destination, 
  * sets the destMap to show that char 
  * 'j' is being used, and
  * calculates how far the char 'i' needs to travel on 
  * each step to get to its destination. */
 for (i = 1; i <= strLength; i++)
 for (j = 1; j <= strLength; j++)
 if ( startString[i] == endString[j] &&
  ! destSwitchMap[j] )
 {
 /* If destSwitchMap[j] is set, then it already has a 
  * char which is using it for a destination. */
 destSwitchMap[j] = true;
 
 /* Remember this char's dest. */
 destMap[i] = j;
 
 /* Find out how far this char should move 
  * on each step. */
 if (i == j)
 distances[i] = 0;
 else
 {
    divResult = div(j - i, numSteps);
    distances[i] = divResult.quot;
 
 /* Use the remainder to make
  * sure this char moves each step.*/ 
    if (divResult.rem != 0)
    if (divResult.rem < 0)
       distances[i] -= 1;
    else
   distances[i] += 1;
 
    /* Increment to exit loop. */
    j = 512;
 }
 }
 
 /* In this loop, each character tries to move towards its 
  * destination. Its distance is then recalculated to 
  * compensate for it being switched. This creates a 
  * 'morphing' effect, where the letters in the start string 
  * gradually change to their positions in the end string. */
 for (i = 0; i < numSteps; i++)
 {
 /* Copy the appropriate string for switching. */
 if (i > 0)
 memcpy(*stepStringPtrs[i],
  *stepStringPtrs[i - 1],
  strLength + 1);
 else
 memcpy(*stepStringPtrs[0], startString,
   strLength + 1);
 
 /* Clear the check list for use. */
 for (k = 1; k <= strLength; k++)
 checkList[k] = false;
 
 /* This loop switches characters until
  * switchPossible = false. */
 do
 {
  switchPossible = false;

  for (j = 1; j <= strLength; j++)
  {
   if (distances[j] != 0 &&
  ! checkList[j])
   {
      /* Calculate this char's intended
 * destination for this step. */
      destination = j + distances[j];
        
      if (checkList[destination])
      {
 /* If the destination has already been used, find 
  * the nearest one to it to switch to. */
          destination = -1;
          
         if (distances[j] > 0)
          for (k = destination - 1; k > j;
  k -= 1)
          if (! checkList[k] &&
  distances[k] != 0)
          {
          destination = k;
          k = 512;
          }
          else;
         else
          for (k = destination + 1; k < j;
  k++)
          if (! checkList[k] &&
  distances[k] != 0)
          {
          destination = k;
          k = 512;
          }
      }
      
      if (destination > 0)
      {
       /* If destination is a valid number, do the 
   * neccessary switching. Switch the characters
   * in the string */
        memSwitch =
   stepStringPtrs[i][0][destination];
        stepStringPtrs[i][0][destination]
   = stepStringPtrs[i][0][j];
        stepStringPtrs[i][0][j] =
   memSwitch;
        
        /* Switch the character's mapped destinations. */
        memSwitch = destMap[destination];
        destMap[destination] = destMap[j];
        destMap[j] = memSwitch;
        
        /* Show that the destination has been switched. */
        checkList[destination] = true;
        
        /* Recalculate the switched char's distance. */
        if (destMap[j] == j)
        distances[j] = 0;
        else if (i + 1 < numSteps)
        {
     divResult = div(destMap[j] - j,
  numSteps - i - 1);
     distances[j] = divResult.quot;
     if (divResult.rem != 0)
     if (divResult.rem < 0)
      distances[j] -= 1;
     else
     distances[j] += 1;
  }
  
    switchPossible = true;
      }
   }
   }
 } while (switchPossible);
 
 if (i + 1 == numSteps)
 return;
 
 /* Recalculate all distances to compensate
  * for switched char's. */
 for (k = 1; k <= strLength; k++)
 if (distances[k] != 0)
 {
 if (destMap[k] == k)
 distances[k] = 0;
 else if (i + 1 < numSteps)
 {
    /* Recalculate how far this char needs to move 
 * with the number of steps that are left. */
    divResult = div(destMap[k] - k,
  numSteps - i - 1);
    distances[k] = divResult.quot;
    if (divResult.rem != 0)
    if (divResult.rem < 0)
    distances[k] -= 1;
    else
    distances[k] += 1;
 }
 }
 }
}

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

PDFKey Pro 4.3 - Edit and print password...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Kodi 15.0.beta1 - Powerful media center...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
DiskCatalogMaker 6.4.12 - Catalog your d...
DiskCatalogMaker is a simple disk management tool which catalogs disks. Simple, light-weight, and fast. Finder-like intuitive look and feel. Super-fast search algorithm. Can compress catalog data... Read more
Macs Fan Control 1.3.0.0 - Monitor and c...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more
Lyn 1.5.11 - Lightweight image browser a...
Lyn is a lightweight and fast image browser and viewer designed for photographers, graphic artists and Web designers. Featuring an extremely versatile and aesthetically pleasing interface, it... Read more
NeoOffice 2014.11 - Mac-tailored, OpenOf...
NeoOffice is a complete office suite for OS X. With NeoOffice, users can view, edit, and save OpenOffice documents, PDF files, and most Microsoft Word, Excel, and PowerPoint documents. NeoOffice 3.x... Read more
LaunchBar 6.4 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Remotix 3.1.4 - Access all your computer...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features Complete Apple Screen Sharing support - including Mac OS X login, clipboard... Read more
DesktopLyrics 2.6.6 - Displays current i...
DesktopLyrics is an application that displays the lyrics of the song currently playing in "iTunes" right on your desktop. The lyrics for the song have to be set in iTunes; DesktopLyrics does nothing... Read more
VOX 2.5.1 - Music player that supports m...
VOX is a beautiful music player that supports many filetypes. The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all... Read more

This Week at 148Apps: May 18-22, 2015
May Days at 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 above the... | Read more »
Biz Builder Delux (Games)
Biz Builder Delux 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: Ah, there's nothing like the rhythmic bustle of a burgeoning business burg... especially when you're the one building it... | Read more »
Auroch Digital is Bringing Back Games Wo...
| Read more »
Blades of Brim is a New Endless Runner f...
SYBO Games, the minds behind the ever-popular Subway Surfers, have announced their latest project: Blades of Brim. [Read more] | Read more »
Carbo - Handwriting in the Digital Age...
Carbo - Handwriting in the Digital Age 1.0 Device: iOS Universal Category: Productivity Price: $3.99, Version: 1.0 (iTunes) Description: | Read more »
Draggy Dead (Games)
Draggy Dead 1.1 Device: iOS Universal Category: Games Price: $.99, Version: 1.1 (iTunes) Description: Ditch your dead end job and take up a rewarding career in Grave Robbing today!Guide the recently deceased to a fun filled life of... | Read more »
Bad Dinos (Games)
Bad Dinos 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: | Read more »
The Apple Watch isn't Great as a Fi...
| Read more »
Show the World What You See With Stre.am...
Live broadcasting is getting popular on mobile devices, which is why you can now get Stre.am, by Infinite Takes. [Read more] | Read more »
PhotoTime's 2.1 Update Adds Apple W...
The latest PhotoTime update is adding even more functionality to the handy photo organizing app. Yep, including Apple Watch support. [Read more] | Read more »

Price Scanner via MacPrices.net

12-inch MacBook stock status for Monday, May...
The new 12″ Retina MacBooks are still on backorder at The Apple Store with a 3-5 week waiting period. However, a few models are in stock today at Apple resellers. Stock is limited, so act now if you’... Read more
New 27-inch 3.3GHz 5K iMac in stock with free...
Adorama has the new 27″ 3.3GHz 5K iMac in stock today for $1999 including free shipping plus NY & NJ sales tax only. Adorama will include a free copy of Apple’s 3-year AppleCare Protection Plan. Read more
Memorial Day Weekend Sale: New 27-inch 3.3GHz...
Best Buy has the new 27″ 3.3GHz 5K iMac on sale for $1899.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary... Read more
OtterBox Maximizes Portability, Productivity...
From the kitchen recipe book to the boarsroom presentation, the OtterBox Agility Tablet System turns tablets into one of the most versatile pieces of handheld technology available. Available now, the... Read more
Launch of New Car App Gallery and Open Develo...
Automatic, a company on a mission to bring the power of the Internet into every car, has announced the launch of the Automatic App Gallery, an app store for nearly every car or truck on the road... Read more
Memorial Day Weekend Sale: 13-inch 1.6GHz Mac...
Best Buy has the new 13″ 1.6GHz/128GB MacBook Air on sale for $849 on their online store this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders... Read more
Memorial Day Weekend Sale: 27-inch 3.5GHz 5K...
Best Buy has the 27″ 3.5GHz 5K iMac on sale for $2099.99 this weekend. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store prices may vary.... Read more
Sale! 16GB iPad mini 3 for $349, save $50
B&H Photo has the 16GB iPad mini 3 WiFi on sale for $349 including free shipping plus NY sales tax only. Their price is $50 off MSRP, and it’s the lowest price available for this model. Read more
Price drop on 2014 15-inch Retina MacBook Pro...
B&H Photo has dropped prices on 2014 15″ Retina MacBook Pros by $200. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799.99 save $200 - 15″ 2.5GHz... Read more
With a Mission to Make Mobile Free, Scratch W...
Scratch Wireless, claiming to be the world’s first truly free mobile service, has announced the availability of a new Scratch-enabled Android smartphone, the Coolpad Arise. The smartphone is equipped... Read more

Jobs Board

Payments Counsel, *Apple* Pay (mobile payme...
**Job Summary** Apple is looking for an atto ey to join Apple 's Legal Department to support Apple Pay. **Key Qualifications** 7+ years of relevant experience Read more
Touch Hardware Design and Integration Enginee...
…Summary** Design, develop, and launch next-generation Touch solutions in the new Apple Watch product category. The Touch team develops cutting-edge Touch solutions and Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* TV Live Streaming Frameworks Test En...
**Job Summary** Work and contribute towards the engineering of Apple 's state-of-the-art products involving video, audio, and graphics in Interactive Media Group (IMG) at Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.