TweetFollow Us on Twitter

Dec 94 Challenge
Volume Number:10
Issue Number:12
Column Tag:Programmer’s Challenge

Programmer’s Challenge

By Mike Scanlin, Mountain View, CA

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

The rules

Here’s how it works: Each month we present a different programming challenge here. First, you write some code that solves the challenge. Second, optimize your code (a lot). Then, submit your solution to MacTech Magazine. We choose a winner 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, we’ll choose one winner at random (with honorable mention, but no prize, given to the runners up). The prize for each month’s best solution is $50 and a limited-edition “The Winner! MacTech Magazine Programming Challenge” T-shirt (not available in stores).

To help us make fair comparisons, all solutions must be in ANSI compatible C (e.g. don’t use Think’s Object extensions). Use only pure C code. We disqualify any entries with any assembly in them (except for challenges specifically stated to be in assembly). You may call any routine in the Macintosh toolbox (e.g., it doesn’t matter if you use NewPtr instead of malloc). We test entries with the FPU and 68020 flags turned off in THINK C. We time routines with the latest THINK C (with “ANSI Settings”, “Honor ‘register’ first”, and “Use Global Optimizer” turned on), so beware if you optimize for a different C compiler. Limit your code to 60 characters wide. This helps with e-mail gateways and page layout.

We publish the solution and winners for this month’s Programmers’ Challenge two months later. All submissions must be received by the 10th day of the month printed on the front of this issue.

Mark solutions “Attn: Programmers’ Challenge Solution” and send them via e-mail - Internet progchallenge@xplain.com, AppleLink MT.PROGCHAL, CompuServe 71552,174 and America Online MT PRGCHAL. Include the solution, all related files, and your contact info. If you send via snail mail, send a disk with those items on it; see “How to Contact Us” on p. 2.

MacTech Magazine reserves the right to publish any solution entered in the Programming Challenge of the Month. Authors grant MacTech Magazine the non-exclusive right to publish entries without limitation upon submission of each entry. Authors retain copyrights for the code.

Rubik’s Cube

There are several things I’m good at. Solving Rubik’s Cube isn’t one of them. One of my sadist friends gave me one last Christmas. I scramble it all the time and leave it on my desk at work. Then I watch in amazement as any one of several co-workers walks up to it and solves it within the amount of time it takes to ask “Mike, what’s the fastest way to do buffered file I/O?” It’s very frustrating.

This month’s challenge idea comes not only from my own inadequacy but also from Jim Lloyd (Mountain View, CA). The goal is to solve Rubik’s Cube.

The prototype of the function you write is:


/* 1 */
int
SolveRubiksCube(cubePtr)
RubiksCube*cubePtr;

Since I am so pathetic at solving the cube, I do not have enough insight to design an effective data structure to represent it. You get to define the RubiksCube typedef anyway you like.

Each call to SolveRubiksCube should make exactly one move. A move means turning any side any direction by 90 degrees. The function returns one of 3 values on each call to it:


/* 2 */
 -1   illegal cube condition, can’t be solved
  0   made a move, but not done yet
  1   made the last move, it’s solved

Your routine will be called in a loop from my test bench something like this:


/* 3 */
ScrambleCube(cubePtr);
do {
 x = SolveRubiksCube(cubePtr);
} while (x == 0);

Minimizing the number of moves to solve the cube is not important. Minimizing the total time required to solve the cube is important. If your SolveRubiksCube routine needs to keep track of some kind of state info or cached solution info between calls to it then it may use static variables to do so (or, you could incorporate that info into the RubiksCube data structure).

It is not required to detect an illegal cube condition on the first call to SolveRubiksCube, just so long as it is detected eventually (i.e. don’t go into an infinite loop if someone removes a couple of squares from your cube and puts them back in such a way that it makes the cube unsolvable).

Because I will need to be able to watch your routine’s progress, you will need to write two conversion routines:


/* 4 */
void
MikeCubeToRubiksCube(mikePtr, rubikPtr)
MikeCube*mikePtr;
RubiksCube*rubikPtr;

void
RubiksCubeToMikeCube(rubikPtr, mikePtr)
RubiksCube*rubikPtr;
MikeCube*mikePtr;

The purpose is to convert your cube from whatever data structure you come up with into something my test bench can understand. It only knows about MikeCubes:


/* 5 */
typedef struct CubeSide {
 char   littleSquare[3][3];
} CubeSide;

typedef struct MikeCube {
 CubeSide face[6];
} MikeCube;

A cube has 6 CubeSides. If you look at a cube straight on then the indexes are: 0 = top, 1 = left side, 2 = front, 3 = right side, 4 = bottom, 5 = back. Within each CubeSide there is a 3x3 array of littleSquares (first index is row, second index is column). Each littleSquare is a number from 0 to 5, where each number represents one of the 6 colors that make up a cube.

So, a solved cube would have all 9 of the littleSquares for each side set to the same value. A solved cube that had the rightmost vertical column rotated counterclockwise 90 degrees would look like this:

   005
   005
   005
111220333
111220333
111220333
   442
   442
   442
   554
   554
   554

The top part (the 005 lines) represent the top of the cube after the rotation. The 220 pieces are what you see on the front, the 442 lines are what you see on the bottom and the 554 pieces are what’s on the back. The value of mikePtr-> face[0]. littleSquare[1][2] is 5. The value of mikePtr->face[0].littleSquare[1][1] is 0 (the center square of the top).

Write to me if you have questions on this. Your conversion routines are not going to be part of your times so it doesn’t matter if they’re slow. Have fun.

Two Months Ago Winner

Based on the number of entries I received for the How Long Will It Take Challenge I would have to say that software time estimates are even more difficult than their well-deserved reputation implies. Either that or the typical Programmer Challenge entrant isn’t concerned with schedules (or, at least, this Challenge). In any case, congrats (and thanks) to Jeremy Vineyard (Lawrence, KS) for winning. I suppose the fact that he was the only person to enter helped his entry somewhat but there are signs of some careful thinking in his entry as well. (Although I must confess that I find the inclusion of a Jolt Cola parameter completely useless. Mountain Dew on the other hand...) This is Jeremy’s second 1st place showing (he also won the Insane Anglo Warlord challenge in February, 1993). Nice job!

Jeremy’s entry refers to a book by E. Barne called “Estimation of Time-Space Development Theorems” which I wasn’t, unfortunately, able to track down before my column deadline. Sounds like something to check out, though, if you’re involved with scheduling.

Here’s Jeremy’s winning solution:

Top 5 Excuses Why This Project Was Late:

1. “I though you said it was due NEXT month!”

2. The Product Manager quit after we missed the beta acceptance deadline.

3. Somebody activated the fire alarm while we were holding a brainstorming session, and all our ideas were lost.

4. QA didn’t keep us up to date on active bugs.

5. I just couldn’t wait to try out the new game of solitaire that came with System 7.5!

The skill of the product manager is the key to a successful product.

 
/* 6 */
enum {
 // Manager ratings. 
 noManager = 0,
 lazyManager = 1,
 poorManager = 2,
 okManager = 3,
 motivatedManager = 4,
 excellentManager = 5
};

enum {
 // System versions. 
 system7 = 7,
 system6 = 6,
 system5 = 5,
 system4 = 4,
 system3 = 3,
 system2 = 2,
 system1 = 1
};


// It assumed that the better the manager is, the more lines
// the engineers will be motivated to write.
#define juniorLines(100 + (20 * manager))
#define seniorLines(200 + (25 * manager))

// Every large project will have an overhead for planning,
// designing, and preparing for development.
#define overhead (linesC / 5000)

// These ratios are based on Barne’s matrix equations
// related to the study of time-space software development
// theorems. (trust me!)
#define PPCNativeRatio    (float) (1.75 - (.02 * powerMacs))
#define joltRatio(float) (.7)
#define systemSupportRatio(float) (7.0 / systemSupport)

// Here again,the manager can motivate both QA and UI
// people to be more productive.
#define qaRatio  1 - (.1 + (.01 * manager) * qaPeople)
#define uiRatio  (float) ((1.2 - \
 (.01 * manager)) * (seniorEng - uiPeople))

// Localization- a nightmare. Enough said.
#define localizedRatio    (float) (1.35 * localized)

SoftwareTimeEstimate

A simplified algorithm that accurately calculates the time in calendar days for any Macintosh software product to be completed.

The complete algorithm and collection of equations can be found in E. Barne’s Estimation of Time-Space Development Theorems, published by Academic Press.

Implementation by Jeremy Vineyard, Lawrence, KS


/* 7 */
SoftwareTimeEstimate

unsigned short SoftwareTimeEstimate(linesC, seniorEng,
 juniorEng, systemSupport, PPCNative, powerMacs, manager,
 jolt, qaPeople, uiPeople, localized)
 
 // Estimated # lines of source code in C.
 unsigned long linesC;

 // # of competent engineers with more than 5
 // years experience.
 unsigned short seniorEng;
 
 // # of junior engineers with less than 2
 // years experience.
 unsigned short juniorEng;

 // Earliest version of system software supported by
 // product (1-7)
 unsigned short systemSupport;

 // TRUE if product will be PowerPC native.
 Boolean PPCNative;
 
 // # of PowerMacs available to developers (1-30).
 unsigned short powerMacs;

 // Rating of manager 1-5 (1 is poor, 5 is excellent)
 // or 0 if none.
 unsigned short manager;

 // TRUE if company has steady supply of Jolt cola.
 Boolean jolt;   
 
 // # of trained, in-house testers (most important).
 unsigned short qaPeople;
 
 // # of people responsible for making decisions about UI.     
 unsigned short uiPeople;
 
 // # of Languages product must be localized to before
 // shipping or 0 if none.
 unsigned short localized;
{
 float  time, ratio;
 short  linesADay;
 

 // Calculate the lines of source code that can be 
 // produced per day based upon the number of engineers 
 // working on the product.
 // (Must have at least one engineer)
 linesADay = (seniorEng * seniorLines) 
  + (juniorEng * juniorLines);
 
 // Estimate the # of days it will take to produce the   
 // specified amount of code. 
 time = (linesC / linesADay) + overhead;
 
 // The farther backwards this product is compatible with      
 
 // system versions, the more time it will take to develop.    
 
 // systemSupport should be from 1 (System 1.0) to 7.
 time *= systemSupportRatio;
 
 // More development & QA time will need to be spent on  
 // a product that is PowerPC native. The more Power Macs
 // that are available to developers, the faster the 
 // development & testing process will proceed.                
 
 if (PPCNative)
 time *= PPCNativeRatio;
 
 // o JOLT COLA!  o
 // o GIve the PRogramMeRS that EXtra ZING! to geT thEm o
 // o MOTIVATED!! o
 if (jolt)
 time *= joltRatio;

 // Quality assurance is one of the most important             
 // aspects of a product’s construction.  Without it, the      
 
 // product will fail to reach the user base because of 
 // too many bugs. QA can never be overstaffed!                
 
 time *= qaRatio;

 // User interface has a limited potential because people      
 // are likely to have very set opinions, and if there 
 // are too many UI people, it can kill a product. There       
 // should never be more UI personnel than engineers.    
 if (uiPeople > seniorEng)
 time *= uiRatio;

 // The more languages the product must be localized to
 // before it can be shipped has a drastic effect on the
 // development time.
 if (localized)
 time *= localizedRatio;
 
 return (short) time;
}







  
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Macs Fan Control 1.3.1.0 - 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
NetShade 6.3.1 - Browse privately using...
NetShade is an anonymous proxy and VPN app+service for Mac. Unblock your Internet through NetShade's high-speed proxy and VPN servers spanning seven countries. NetShade masks your IP address as you... Read more
Dragon Dictate 4.0.7 - Premium voice-rec...
With Dragon Dictate speech recognition software, you can use your voice to create and edit text or interact with your favorite Mac applications. Far more than just speech-to-text, Dragon Dictate lets... Read more
Persecond 1.0.2 - Timelapse video made e...
Persecond is the easy, fun way to create a beautiful timelapse video. Import an image sequence from any camera, trim the length of your video, adjust the speed and playback direction, and you’re done... Read more
GIMP 2.8.14p2 - Powerful, free image edi...
GIMP is a multi-platform photo manipulation tool. GIMP is an acronym for GNU Image Manipulation Program. The GIMP is suitable for a variety of image manipulation tasks, including photo retouching,... Read more
Sandvox 2.10.2 - Easily build eye-catchi...
Sandvox is for Mac users who want to create a professional looking website quickly and easily. With Sandvox, you don't need to be a Web genius to build a stylish, feature-rich, standards-compliant... Read more
LibreOffice 5.0.1.2 - 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
f.lux 36.1 - Adjusts the color of your d...
f.lux makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day. Ever notice how people texting at night have that eerie blue glow? Or wake... Read more
VirtualBox 5.0.2 - x86 virtualization so...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
File Juicer 4.43 - 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. In computer... Read more

ReBoard: Revolutionary Keyboard (Utilit...
ReBoard: Revolutionary Keyboard 1.0 Device: iOS Universal Category: Utilities Price: $1.99, Version: 1.0 (iTunes) Description: Do everything within the keyboard without switching apps! If you are in WhatsApp, how do you schedule a... | Read more »
Tiny Empire (Games)
Tiny Empire 1.1.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1.3 (iTunes) Description: Launch cannonballs and blow tiny orcs into thousands of pieces in this intuitive fantasy-themed puzzle shooter! Embark on an... | Read more »
Astropad Mini (Productivity)
Astropad Mini 1.0 Device: iOS iPhone Category: Productivity Price: $4.99, Version: 1.0 (iTunes) Description: *** 50% off introductory price! ​*** Get the high-end experience of a Wacom tablet at a fraction of the price with Astropad... | Read more »
Emo Chorus (Music)
Emo Chorus 1.0.0 Device: iOS Universal Category: Music Price: $1.99, Version: 1.0.0 (iTunes) Description: Realistic Choir simulator ranging from simple Chorus emulation to full ensemble Choir with 128 members. ### introductory offer... | Read more »
Forest Spirit (Games)
Forest Spirit 1.0.5 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.5 (iTunes) Description: | Read more »
Ski Safari 2 (Games)
Ski Safari 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The world's most fantastical, fun, family-friendly skiing game is back and better than ever! Play as Sven's sister Evana, share... | Read more »
Lara Croft GO (Games)
Lara Croft GO 1.0.47768 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.47768 (iTunes) Description: Lara Croft GO is a turn based puzzle-adventure set in a long-forgotten world. Explore the ruins of an ancient... | Read more »
Whispering Willows (Games)
Whispering Willows 1.23 Device: iOS Universal Category: Games Price: $4.99, Version: 1.23 (iTunes) Description: **LAUNCH SALE 50% OFF** - Whispering Willows is on sale for 50% off ($4.99) until September 9th. | Read more »
Calvino Noir (Games)
Calvino Noir 1.1 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: The film noir stealth game. Calvino Noir is the exploratory, sneaking adventure through the 1930s European criminal underworld.... | Read more »
Angel Sword (Games)
Angel Sword 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Prepare to adventure in the most epic full scale multiplayer 3D RPG for mobile! Experience amazing detailed graphics in full HD.... | Read more »

Price Scanner via MacPrices.net

iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
MacBook Airs on sale for $100 off MSRP
Best Buy has MacBook Airs on sale for $100 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary... Read more
Big Grips Lift Handle For iPad Air and iPad A...
KEM Ventures, Inc. which pioneered the extra-large, super-protective iPad case market with the introduction of Big Grips Frame and Stand in 2011, is launching Big Grips Lift featuring a new super-... Read more
Samsung Launches Galaxy Tab S2, Its Most Powe...
Samsung Electronics America, Inc. has announced the U.S. release of the Galaxy Tab S2, its thinnest, lightest, ultra-fast tablet. Blending form and function, elegant design and multitasking power,... Read more
Tablet Screen Sizes Expanding as iPad Pro App...
Larger screen sizes are gaining favor as the tablet transforms into a productivity device, with shipments growing 185 percent year-over-year in 2015. According to a new Strategy Analytics’ Tablet... Read more
Today Only: Save US$50 on Adobe Elements 13;...
Keep the memories. lose the distractions. Summer’s winding down and it’s time to turn almost perfect shots into picture perfect memories with Elements 13. And get the power to edit both photos and... Read more
1.4GHz Mac mini on sale for $449, save $50
Best Buy has the 1.4GHz Mac mini on sale for $50 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Price for online orders only, in-store price may vary... Read more
12-inch 1.1GHz Gold MacBook on sale for $1149...
B&H Photo has the 12″ 1.1GHz Gold Retina MacBook on sale for $1149.99 including free shipping plus NY sales tax only. Their price is $150 off MSRP, and it’s the lowest price available for this... Read more
27-inch 3.3GHz 5K iMac on sale for $1849, sav...
Best Buy has the 27″ 3.3GHz 5K iMac on sale for $1849.99. Their price is $150 off MSRP, and it’s the lowest price available for this model. Choose free shipping or free local store pickup (if... Read more
Worldwide Tablet Shipments Expected to Declin...
Does Apple badly need a touchscreen convertible/hybrid laptop MacBook? Yes, judging from a new market forecast from the International Data Corporation (IDC) Worldwide Quarterly Tablet Tracker, which... Read more

Jobs Board

*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
*Apple* Retail Online Store: Customer Insigh...
**Job Summary** Apple Retail (Online Store) is seeking an experienced e-commerce analytics professional to join the Customer Insights Team. The Web e-Commerce Analyst Read more
*Apple* Music, Business Operations - Apple I...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
WW *Apple* Retail Online Store: Customer In...
**Job Summary** The Apple Retail - Online Store is seeking an experienced web merchandising analytics professional to join the Customer Insights Team. The Web Read more
Senior Payments Security Manager - *Apple*...
**Job Summary** Apple , Inc. is looking for a highly motivated, innovative and hands-on senior payments security manager to join the Apple Pay security team. You will Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.