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
$116.47
Apple Inc.
+0.00
MSFT
$47.98
Microsoft Corpora
+0.00
GOOG
$537.50
Google Inc.
+0.00

MacTech Search:
Community Search:

Software Updates via MacUpdate

Cobook 3.0.7 - Intelligent address book....
Cobook Contacts is an intuitive, engaging address book. Solve the problem of contact management with Cobook Contacts and its simple interface and powerful syncing and integration possibilities.... Read more
StatsBar 1.9 - Monitor system processes...
StatsBar gives you a comprehensive and detailed analysis of the following areas of your Mac: CPU usage Memory usage Disk usage Network and bandwidth usage Battery power and health (MacBooks only)... Read more
Cyberduck 4.6 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
Evernote 6.0.1 - Create searchable notes...
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
calibre 2.11 - Complete e-library manage...
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
Herald 5.0.1 - Notification plugin for M...
Note: Versions 2.1.3 (for OS X 10.7), 3.0.6 (for OS X 10.8), and 4.0.8 (for OS X 10.9) are no longer supported by the developer. Herald is a notification plugin for Mail.app, Apple's Mac OS X email... Read more
Firetask 3.7 - Innovative task managemen...
Firetask uniquely combines the advantages of classical priority-and-due-date-based task management with GTD. Stay focused and on top of your commitments - Firetask's "Today" view shows all relevant... Read more
TechTool Pro 7.0.6 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
PhotoDesk 3.0.1 - Instagram client for p...
PhotoDesk lets you view, like, comment, and download Instagram pictures/videos! (NO Uploads! / Image Posting! Instagram forbids that! AND you *need* an *existing* Instagram account). But you can do... Read more

Latest Forum Discussions

See All

Space Expedition Review
Space Expedition Review By Jordan Minor on November 24th, 2014 Our Rating: :: ONE SMALL STEPUniversal App - Designed for iPhone and iPad The only thing boring about Space Expedition’s lonely journey is its title.   | Read more »
Ubisoft Gives Everyone Two New Ways to E...
Ubisoft Gives Everyone Two New Ways to Earn In-Game Stuff for Far Cry 4 Posted by Jessica Fisher on November 21st, 2014 [ permalink ] | Read more »
Golfinity – Tips, Tricks, Strategies, an...
Dig this: Would you like to know what we thought of being an infinite golfer? Check out our Golfinity review! Golfinity offers unlimited ways to test your skills at golf. Here are a few ways to make sure your score doesn’t get too high and your... | Read more »
Dark Hearts, The Sequel to Haunting Meli...
Dark Hearts, The Sequel to Haunting Melissa, is Available Now Posted by Jessica Fisher on November 21st, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Meowza! Toyze Brings Talking Tom to Life...
Meowza! | Read more »
Square Enix Announces New Tactical RPG f...
Square Enix Announces New Tactical RPG for Mobile, Heavenstrike Rivals. Posted by Jessica Fisher on November 21st, 2014 [ permalink ] With their epic stories and gorgeous graphics, | Read more »
Quest for Revenge (Games)
Quest for Revenge 1.0.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.0 (iTunes) Description: The great Kingdom of the west has fallen. The gods ignore the prayers of the desperate. A dark warlord has extinguished... | Read more »
Threadz is a New Writing Adventure for Y...
Threadz is a New Writing Adventure for You and Your Friends Posted by Jessica Fisher on November 21st, 2014 [ permalink ] In the tradition of round-robin storytelling, | Read more »
SteelSeries Stratus XL Hardware Review
Made by: SteelSeries Price: $59.99 Hardware/iOS Integration Rating: 4 out of 5 stars Usability Rating: 4.5 out of 5 stars Reuse Value Rating: 4.25 out of 5 stars Build Quality Rating: 4.5 out of 5 stars Overall Rating: 4.31 out of 5 stars | Read more »
ACDSee (Photography)
ACDSee 1.0.0 Device: iOS iPhone Category: Photography Price: $1.99, Version: 1.0.0 (iTunes) Description: Capture, perfect, and share your photos with ACDSee. The ACDSee iPhone app combines an innovative camera, a powerful photo... | Read more »

Price Scanner via MacPrices.net

CEA Study Finds More People Recycling Electro...
A new study by the Consumer Electronics Association (CEA) finds that electronics recycling receives the continued and growing support of consumers. According to the CEA,s Recycling and Reuse Study,... Read more
15″ 2.2GHz Retina MacBook Pro on sale for $17...
 B&H Photo has the 2014 15″ 2.2GHz Retina MacBook Pro on sale today for $1749. Shipping is free, and B&H charges NY sales tax only. B&H will also include free copies of Parallels Desktop... Read more
27-inch 3.5GHz 5K iMac in stock today and on...
 B&H Photo has the new 27″ 3.5GHz 5K iMac in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available... Read more
21-inch 1.4GHz iMac on sale for $979, save $1...
B&H Photo has the new 21″ 1.4GHz iMac on sale for $979.99 including free shipping plus NY sales tax only. Their price is $120 off MSRP. B&H will also include free copies of Parallels Desktop... Read more
13-inch 1.4GHz/256GB MacBook Air on sale for...
B&H Photo has lowered their price on the 13″ 1.4GHz/256GB MacBook Air to $1059.99 including free shipping plus NY sales tax only. Their price is $140 off MSRP, and it’s the lowest price for this... Read more
Save up to $400 with Apple refurbished 2014 1...
The Apple Store has restocked Apple Certified Refurbished 2014 15″ Retina MacBook Pros for up to $400 off the cost of new models. An Apple one-year warranty is included with each model, and shipping... Read more
New 13-inch 1.4GHz MacBook Air on sale for $8...
 Adorama has the 2014 13″ 1.4GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY & NJ tax only. Their price is $100 off MSRP. B&H Photo has the 13″ 1.4GHz/128GB MacBook... Read more
Apple Expected to Reverse Nine-Month Tablet S...
Apple and Samsung combined accounted for 62 percent of the nearly 36 million branded tablets shipped in 3Q 2014, according to early vendor shipment share estimates from market intelligence firm ABI... Read more
Stratos: 30 Percent of US Smartphone Owners t...
Stratos, Inc., creator of the Bluetooth Connected Card Platform, has announced results from its 2014 Holiday Mobile Payments Survey. The consumer survey found that nearly one out of three (30 percent... Read more
2014 1.4GHz Mac mini on sale for $449, save $...
 B&H Photo has lowered their price on the new 1.4GHz Mac mini to $449.99 including free shipping plus NY tax only. Their price is $50 off MSRP, and it’s the lowest price available for this new... Read more

Jobs Board

*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)- Retail S...
**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
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
*Apple* Store Leader Program - College Gradu...
Job Description: Job Summary As an Apple Store Leader Program agent, you can continue your education as you major in the art of leadership at the Apple Store. You'll 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.