TweetFollow Us on Twitter

Jun 01 Programmers Challenge

Volume Number: 17 (2001)
Issue Number: 06
Column Tag: Programmer's Challenge

by Bob Boonstra, Westford, MA

Dots

You have probably played the game Dots before, although perhaps not in quite some time. My memory of the game dates back to childhood, when we played it in the car while on some long trip. Greg Sadetsky suggested that Dots might make an interesting Challenge, and he wins two Challenge points for that suggestion.

The game starts with a piece of paper with a rectangular grid of NxN dots. The game proceeds with two players alternating turns connecting adjacent dots with a line. Two dots are adjacent if they are in the same row and in adjacent columns, or in the same column and in adjacent rows. The object of the game is to take possession of more squares than does your opponent. Each time a player connects dots that form the fourth edge of a square, the player takes possession of that square. A line can complete zero, one, or two squares. When a player completes one or more squares, s/he is entitled to make another move, and to continue making additional moves as long as a square is completed with each move. The game continues until every square has been formed.

The prototype for the code you should write is:

typedef struct Dot {
   short row;      /* row number of dot, 0..boardSize-1 */
   short col;      /* column number of dot, 0..boardSize-1 */
} Dot;

typedef struct DotLine {
   Dot dot1;      /* first dot of a line */
   Dot dot2;      /* second dot of a line */
   /*   legal lines are formed by dots in the same row, in adjacent columns, or in the same column 
   in adjacent rows */
} DotLine;         

void InitDots(
   short boardSize,      /* number of dots per row/col in board */
   Boolean playFirst,    /* true if you play first, false of opponent plays first */
   WindowPtr dotWindow   /* color window where you should draw game results */
);

void OpponentMove(
const DotLine opponentLine   /* line formed by your opponent on previous move */
);

short /* number of lines generated   */ PlayDots(
   DotLine yourLines[]         /* return the lines you form here */
);

void TermDots(void);      /* return any storage you allocated */

Play begins with a call to your InitDots routine, where you are given the size of the game board (boardSize), an indicator of who plays first (playFirst), and a pointer to a CWindow (passed as a WindowPtr because that’s what most toolbox routines expect). In that window, you will be required to display the progress of the game as it proceeds.

When it is your turn to move, your PlayDots routine will be called. Your code should select the most advantageous move and return it in yourLines[0]. If that move forms a square, you can select an additional move, store it in yourLines[1], and continue as long as squares are formed. PlayDots should return the number of moves you made during your turn.

After your opponent has played, your OpponentMove routine will be called one or more times, once for each move made by your opponent. The move will be provided in the opponentLine parameter, for use in display and in updating your data structures.

After each of your moves, and after notification of each opponent move, you should display the move and the updated game state in the dotWindow. The window should also display the number of squares completed by each player. The details of the display are left to you, as long as the display is correct.

When all of the squares have been formed, your TermDots routine will be called. You should deallocate any dynamically allocated memory and perform any other cleanup required.

The winner will be determined by a round-robin or other fair tournament played with multiple board sizes. Scoring is based on minimizing your point total, calculated as the number of squares that your opponent occupies, plus a penalty of 1% for each millisecond your solution takes to execute.

The Challenge prize will be divided between the overall winner and the best scoring entry from a contestant that has not won the Challenge recently.

This will be a native PowerPC Challenge, using the CodeWarrior Pro 6 environment. Solutions may be coded in C, C++, or Pascal.

Three Months Ago Winner

Congratulations to Claes Wihlborg for winning the March DragSort Challenge. The object of this Challenge was to sort a list by dragging items from one position to another, minimizing the cumulative distance that the drag cursor traveled while moving to pick up an item and while dragging it to its new position. Four of the five entries I received sorted my test cases correctly, and three of the four used the same basic algorithm. Claes’ entry, however, did so much more efficiently than the others, earning him the Challenge win.

The winning solution moves down the list and picks up the first out-of-order item, dragging it in the same direction and dropping it before the next in-order item. It then continues scanning the list in the same direction, picking up the next out-of-order item and dropping it were it belongs. When it reaches the end of the list, it reverses direction and does the same thing moving backward. It continues to move up and down the list until all of the items are in the correct order. A straightforward and efficient solution.

I evaluated the entries using six test cases using lists ranging up to 6500 elements. Since the problem was based on a hypothetical Usenet application, most of the test cases were based on lists that were ordered correctly except for some relatively small percentage of the list items.

As the best-placing entry from someone who has not won a Challenge in the past two years, Randy Boring wins a share of this month’s Challenge prize. You don’t need to defeat the Challenge points leaders to claim a part of the prize, so enter the Challenge and win Developer Depot credits!

The table below lists, for each of the solutions submitted, the number of penalty points earned by each entry, the total time in milliseconds, and the number of select and drag position moves used to sort the test cases. It also lists the code size, data size, and programming language used for each entry. As usual, the number in parentheses after the entrant’s name is the total number of Challenge points earned in all Challenges prior to this one.

Name Points Time(msecs) Moves
Claes Wihlborg (29) 29026776 180 29026284
Ernst Munter (721) 29026987 706 29026284
Randy Boring (135) 29027737 1456 29026284
Marco Aiello 84384025 4600 84379428
R. O. Incorrect N/A
Name Code Size Data Size Lang
Claes Wihlborg 704 8 C++
Ernst Munter 2380 80 C++
Randy Boring 2212 145 C++
Marco Aiello 1416 28 C++
R. O. 43432 6120 C++

Top Contestants ...

Listed here are the Top Contestants for the Programmer’s Challenge, including everyone who has accumulated 20 or more points during the past two years. The numbers below include points awarded over the 24 most recent contests, including points earned by this month’s entrants, the number of wins over the past 24 months, and the total number of career Challenge points.

Rank Name Points Wins(24 mo) Total Points(24 mo)
1. Munter, Ernst 294 11 731
2. Rieken, Willeke 87 3 134
3. Saxton, Tom 76 2 185
4. Maurer, Sebastian 68 2 108
5. Taylor, Jonathan 56 2 56
6. Shearer, Rob 55 1 62
7. Wihlborg, Claes 49 2 49

... and the Top Contestants Looking for a Recent Win

In order to give some recognition to other participants in the Challenge, we also list the high scores for contestants who have accumulated points without taking first place in a Challenge during the past two years. Listed here are all of those contestants who have accumulated 6 or more points during the past two years.

Rank Name Points(24 mo) Total Points
8. Boring, Randy 39 142
9. Jones, Dennis 12 22
10. Sadetsky, Gregory 12 14
11. Downs, Andrew 12 12
12. Day, Mark 10 30
13. Duga, Brady 10 10
14. Fazekas, Miklos 10 10
15. Flowers, Sue 10 10
16. Strout, Joe 10 10
17. Nicolle, Ludovic 7 55
18. Hala, Ladislav 7 7
19. Miller, Mike 7 7
20. Schotsman, Jan 7 7
21. Widyatama, Yudhi 7 7
22. Heithcock, JG 6 43

There are three ways to earn points: (1) scoring in the top 5 of any Challenge, (2) being the first person to find a bug in a published winning solution or, (3) being the first person to suggest a Challenge that I use. The points you can win are:

1st place 20 points
2nd place 10 points
3rd place 7 points
4th place 4 points
5th place 2 points
finding bug 2 points
suggesting Challenge 2 points

Here is Claes’ winning DragSort solution:

DragSort.cp
Copyright © 2001
Claes Wihlborg

/*
      The program takes a very simple approach and implements
      bubblesort with alternating sort directions.
*/

#include “DragSort.h”

//—————————————————————————————————- DragSort

long /* numMoves */ DragSort(
   long itemsToSort[],   /* array of items to be sorted */
   long numItemsToSort,  /* number of itemsToSort */
   long startPosition,   /* item initially selected */
   Move sortMoves[]      /* store Moves that sort the array here */
)
{
   Move *nextMove = sortMoves;
   
   long temp, temp2;
   
   long *p, *oldp, *pMin, *pMax, *newMin, *newMax;
         
   pMin = itemsToSort;
   pMax = itemsToSort + numItemsToSort - 1;

// If strartpos <> 0, sweep down

   p = itemsToSort + startPosition;
   while( p > pMin )
   {
      oldp = p—;
      
      if( (temp = *oldp) < *p )
      {
         nextMove->selectPosition = oldp - itemsToSort;
         do
         {
            *oldp = *p;
            oldp = p—;
         }
         while( (p >= pMin) && (temp < *p ) );
         nextMove++->dragToPosition =  oldp - itemsToSort;
         *oldp = temp;
      }
   }
   
// 1:st iteration: sweep once up and once down.
// this iteration puts at least the smallest and the biggest items in place. 

   newMax = 0;
   newMin = 0;
   
   p = pMin;
   while( p < pMax ) //sweep up
   {
      oldp = p++;
      
      if( (temp = *oldp) > (temp2 = *p) )
      {
         nextMove->selectPosition = oldp - itemsToSort;
         do
         {
            *oldp = temp2;
            oldp = p++;
         }
         while( (p <= pMax) && (temp > (temp2 = *p)) );
         nextMove++->dragToPosition =  oldp - itemsToSort;
         *oldp = temp;
         newMax = oldp;
      }
   }
   
   if( !newMax ) return nextMove - sortMoves;
        // no more items in wrong order
   
   pMax = newMax - 1;
   p = pMax;
   while( p > pMin ) //sweep down
   {
      oldp = p—;
      
      if( (temp = *oldp) < (temp2 = *p) )
      {
         nextMove->selectPosition = oldp - itemsToSort;
         do
         {
            *oldp = temp2;
            oldp = p—;
         }
         while( (p >= pMin) && (temp < (temp2 = *p)) );
         nextMove++->dragToPosition =  oldp - itemsToSort;
         *oldp = temp;
         newMin = oldp;
      }
   }
   
   if( !newMin ) return nextMove - sortMoves;
        // no more items in wrong order
   pMin = newMin + 1;

   do //main loop: sweep once up and once down for every iteration
   {
      newMax = 0;
      newMin = 0;
      
      p = pMin;
      
      while( p < pMax ) //sweep up
      {
         oldp = p++;
         
         if( (temp = *oldp) > (temp2 = *p) )
         {
            nextMove->selectPosition = oldp - itemsToSort;
            do
            {
               *oldp = temp2;
               oldp = p++;
            }
            while( temp > (temp2 = *p) );
                //simpler condition as biggest element in correct place
            nextMove++->dragToPosition =  oldp -  itemsToSort;
            *oldp = temp;
            newMax = oldp;
         }
      }
      
      if( !newMax ) break;  // no more items in wrong order
      
      pMax = newMax - 1;
      p = pMax;
      
      while( p > pMin ) //sweep down
      {
         oldp = p—;
         
         if( (temp = *oldp) < (temp2 = *p) )
         {
            nextMove->selectPosition = oldp - itemsToSort;
            do
            {
               *oldp = temp2;
               oldp = p—;
            }
            while( temp < (temp2 = *p) );
                   //simpler condition as smallest element in correct place
            nextMove++->dragToPosition =  oldp - itemsToSort;
            *oldp = temp;
            newMin = oldp;
         }
      }
      
      pMin = newMin + 1;
   }
   while( newMin );

   return nextMove - sortMoves;
}
 
AAPL
$101.32
Apple Inc.
+0.74
MSFT
$45.15
Microsoft Corpora
-0.07
GOOG
$582.56
Google Inc.
-0.81

MacTech Search:
Community Search:

Software Updates via MacUpdate

calibre 2.0.0 - Complete e-library manag...
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... Read more
Apple iMovie 10.0.5 - Edit personal vide...
With an all-new design, Apple iMovie lets you enjoy your videos like never before. Browse your clips more easily, instantly share your favorite moments, and create beautiful HD movies and Hollywood-... Read more
Apple Keynote 6.2.2 - Apple's prese...
Apple Keynote makes it simple to create and deliver beautiful presentations. Powerful tools and dazzling effects bring your ideas to life. You can work seamlessly between Mac and iOS devices. And... Read more
Apple Numbers 3.2.2 - Apple's sprea...
With Apple Numbers, sophisticated spreadsheets are just the start. The whole sheet is your canvas. Just add dramatic interactive charts, tables, and images that paint a revealing picture of your data... Read more
OpenOffice 4.1.1 - Free and open-source...
OpenOffice.org is both an Open Source product and a project. The product is a multi-platform office productivity suite. It includes the key desktop applications, such as a word processor,... Read more
Pages 5.2.2 - Apple's word processo...
Apple Pages is a powerful word processor that gives you everything you need to create documents that look beautiful. And read beautifully. It lets you work seamlessly between Mac and iOS devices. And... Read more
Quicken 2015 2.0.1 - Complete personal f...
The new Quicken 2015 helps you manage all your personal finances in one place, so you can see where you're spending and where you can save. Quicken automatically categorizes your financial... Read more
CleanMyMac 2.2.7 - Delete files that was...
CleanMyMac makes space for the things you love. Sporting a range of ingenious new features, CleanMyMac 2 lets you safely and intelligently scan and clean your entire system, delete large, unused... Read more
MacFamilyTree 7.2.4 - Create and explore...
MacFamilyTree gives genealogy a facelift: it's modern, interactive, incredibly fast, and easy to use. We're convinced that generations of chroniclers would have loved to trade in their genealogy... Read more
Videobox 4.1.1 - Download Flash video th...
Videobox allows you to quickly and easily download Flash video from most all of the popular video sites on the internet. Videobox will convert the video into a native Quicktime format so it's ready... Read more

Latest Forum Discussions

See All

Trolls vs Vikings Update Adds Over One H...
Trolls vs Vikings Update Adds Over One Hundred Levels, Reduces Item Cost, and More Posted by Ellis Spice on August 22nd, 2014 [ permalink ] | Read more »
SNK Celebrates the 20th Anniversary of T...
SNK Celebrates the 20th Anniversary of The King of Fighters With a Big Sale Posted by Ellis Spice on August 22nd, 2014 [ permalink ] | Read more »
It Came From Canada: Star Wars: Commande...
With a brand new Star Wars trilogy on the horizon, prepare yourselves for Disney and George Lucas’s space fantasy throwback to be more omnipresent than ever before. So it should come as no surprise that new adventures in that galaxy far, far away... | Read more »
Swing Copters Review
Swing Copters Review By Jordan Minor on August 22nd, 2014 Our Rating: :: DIE TRYINGUniversal App - Designed for iPhone and iPad The creator of Flappy Bird is back with a vengeance.   | Read more »
The Outcast Review
The Outcast Review By Nadia Oxford on August 22nd, 2014 Our Rating: :: HANDS OFF. WAY OFF.Universal App - Designed for iPhone and iPad It’s easy to see what The Outcast is trying for, but its execution needs a lot of work.   | Read more »
Brain+ Review
Brain+ Review By Nadia Oxford on August 22nd, 2014 Our Rating: :: DIM BULBUniversal App - Designed for iPhone and iPad Brain+ is just another entry in an over-saturated brain-training marketplace – and not a particularly fun entry... | Read more »
The Witcher Battle Arena – New Gameplay...
The Witcher Battle Arena – New Gameplay Trailer Revealed Posted by Jessica Fisher on August 22nd, 2014 [ permalink ] Based in the Witcher universe, | Read more »
Max Gentlemen Review
Max Gentlemen Review By Jennifer Allen on August 22nd, 2014 Our Rating: :: OUTSTAYING ITS WELCOMEiPhone App - Designed for the iPhone, compatible with the iPad Max Gentlemen seems pretty quirky initially but that appeal wears thin... | Read more »
Club Penguin Gets Frozen All Over in Lat...
Club Penguin Gets Frozen All Over in Latest Takeover Event Posted by Ellis Spice on August 22nd, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Doctor Who: Legacy Review
Doctor Who: Legacy Review By Jennifer Allen on August 22nd, 2014 Our Rating: :: RUN OF THE MILLUniversal App - Designed for iPhone and iPad Doctor Who: Legacy is an ok match-3 puzzle game, but it lacks some much needed personality... | Read more »

Price Scanner via MacPrices.net

Leftover 15-inch 2.0GHz Retina MacBook Pros a...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros now available for $1599 including free shipping plus NY sales tax only. Their price is $400 off original MSRP. B&H... Read more
Pro.Calendar – New Productivity App for iPad...
Austin, Texas based mobile business and productivity app developer LightArrow, Inc. has announced Pro.Calendar, a powerful and intuitive calendar app with eight versatile calendar options including... Read more
SanDisk Ultra II SSD — Supercharge Your Syste...
SanDisk Corporation has announced the new SanDisk Ultra II SSD with enhanced SSD Dashboard. The new drive is designed to deliver a cost-effective and easy upgrade solution for PC owners looking to... Read more
Samsung and Barnes & Noble Introduce New...
Samsung Electronics America and NOOK Media, a subsidiary of Barnes & Noble, Inc. have announced the introduction of the new Samsung Galaxy Tab 4 NOOK, a 7-inch tablet combining Samsung’s leading... Read more
21-inch iMacs on sale for up to $150 off MSRP
B&H Photo has 21″ iMacs on sale for up to $150 off MSRP including free shipping plus NY sales tax only. B&H will also include a free copy of Parallels Desktop software: - 21″ 2.7GHz iMac: $... Read more
27-inch 3.2GHz iMac on sale for $1698, save $...
Abt has the 27″ 3.2GHz iMac on sale for $1698 including free shipping. Their price is $101 off MSRP. Read more
Mac Backup Guru 2.0 Drive Backup/Cloneing Uti...
Mac Backup Guru developer MacDaddy has released Mac Backup Guru 2.0, offering new and enhanced advanced features, such as bootable backups, synchronised volumes and folders, and a Snapshot mode that... Read more
Operate GE’s New Free-Standing KItchen Range...
Think you accidentally left the oven on? Switch it off while on the go. The new free-standing Profile™ Series gas and electric ranges are GE’s second cooking appliances, following their wall oven, to... Read more
Parallels Announces Parallels Desktop 10 for...
The no. 1-selling software for running Windows applications on a Mac becomes an even easier choice for millions of consumers and IT professionals worldwide with the launch of the most powerful... Read more
Apple now offering certified refurbished 2014...
 The Apple Store is now offering Apple Certified Refurbished 2014 MacBook Airs for up to $180 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more

Jobs Board

Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work 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
Position Opening at *Apple* - Apple (United...
**Job Summary** As more and more people discover Apple , they visit our stores seeking ways to incorporate our products into their lives. It's your job, as a Store Read more
Position Opening at *Apple* - Apple (United...
…Summary** As a Specialist, you help create the energy and excitement around Apple products, providing the right solutions and getting products into customers' hands. You Read more
Project Manager, *Apple* Financial Services...
**Job Summary** Apple Financial Services (AFS) offers consumers, businesses and educational institutions ways to finance Apple purchases. We work with national and Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.