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;
}
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

FINAL FANTASY Ⅸ (Games)
FINAL FANTASY Ⅸ 1.0.4 Device: iOS Universal Category: Games Price: $16.99, Version: 1.0.4 (iTunes) Description: ==========●Special sale price for the FINAL FANTASY IX release! ●20% off from February 10 to February 21, 2016... | Read more »
Tennis Club Story (Games)
Tennis Club Story 1.03 Device: iOS Universal Category: Games Price: $4.99, Version: 1.03 (iTunes) Description: Aim for the ace position of tennis club prestige in this simulation! Your leadership decides if players make it to the big... | Read more »
Check out the new Pirate Attack update i...
Love pirates and board games? Well, you'll love the new Pirate Attack themed update that just launched in Game of Dice. It adds a bunch of new content themed around pirates, like an all new event map based on a pirate ship which revamps the toll... | Read more »
Splash Cars guide - How to paint the tow...
Splash Cars is an arcade driving game that feels like a hybrid between Dawn of the Plow and Splatoon. In it, you'll need to drive a car around to repaint areas of a town that have lost all of their color. Check out these tips to help you perform... | Read more »
The best video player on mobile
We all know the stock video player on iOS is not particularly convenient, primarily because it asks us to hook a device up to iTunes to sync video in a world that has things like Netflix. [Read more] | Read more »
Four apps to help improve your Super Bow...
Super Bowl Sunday is upon us, and whether you’re a Panthers or a Broncos fan you’re no doubt gearing up for it. [Read more] | Read more »
LooperSonic (Music)
LooperSonic 1.0 Device: iOS Universal Category: Music Price: $4.99, Version: 1.0 (iTunes) Description: LooperSonic is a multi-track audio looper and recorder that will take your loops to the next level. Use it like a loop pedal to... | Read more »
Space Grunts guide - How to survive
Space Grunts is a fast-paced roguelike from popular iOS developer, Orange Pixel. While it taps into many of the typical roguelike sensibilities, you might still find yourself caught out by a few things. We delved further to find you some helpful... | Read more »
Dreii guide - How to play well with othe...
Dreii is a rather stylish and wonderful puzzle game that’s reminiscent of cooperative games like Journey. If that sounds immensely appealing, then you should immediately get cracking and give it a whirl. We can offer you some tips and tricks on... | Read more »
Kill the Plumber World guide - How to ou...
You already know how to hop around like Mario, but do you know how to defeat him? Those are your marching orders in Kill the Plumber, and it's not always as easy as it looks. Here are some tips to get you started. This is not a seasoned platform... | Read more »

Price Scanner via MacPrices.net

Apple refurbished 15-inch Retina MacBook Pros...
Apple has Certified Refurbished 2015 15″ Retina MacBook Pros available for up to $380 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free: - 15″ 2... Read more
BookBook For iPad Pro Coming Soon
The iPad Pro is a device unlike any other, and with Apple Pencil, it’s the ideal portable sketchpad: all that’s missing is the modern easel and portfolio to go. TwelveSouth’s BookBook for iPad Pro... Read more
12-inch 1.2GHz Silver Retina MacBook on sale...
B&H Photo has the 12″ 1.2GHz Silver Retina MacBook on sale for $1399 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price for this model from... Read more
iPads on sale at Target: $100 off iPad Air 2,...
Target has WiFi iPad Air 2s and iPad mini 4s 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 for... Read more
Target offers Apple Watch for $100 off MSRP
Target has Apple Watches on sale for $100 for a limited time. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - Apple... Read more
Apple refurbished 2014 13-inch Retina MacBook...
Apple has Certified Refurbished 2014 13″ Retina MacBook Pros available for up to $400 off original MSRP, starting at $979. An Apple one-year warranty is included with each model, and shipping is free... Read more
Macs available for up to $300 off MSRP, $20 o...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Watch Super Bowl 50 Live On Your iPad For Fre...
Watch Super Bowl 50 LIVE on the CBS Sports app for iPad and Apple TV. Get the app and then tune in Sunday, February 7, 2016 at 6:30 PM ET to catch every moment of the big game. The CBS Sports app is... Read more
Two-thirds Of All Smart Watches Shipped In 20...
Apple dominated the smart watch market in 2015, accounting for over 12 million units and two-thirds of all shipments according to Canalys market research analysts’ estimates. Samsung returned to... Read more
12-inch 1.2GHz Retina MacBooks on sale for up...
B&H Photo has 12″ 1.2GHz Retina MacBooks on sale for $180 off MSRP. Shipping is free, and B&H charges NY tax only: - 12″ 1.2GHz Gray Retina MacBook: $1499 $100 off MSRP - 12″ 1.2GHz Silver... 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 - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Subject Matter Expert - Experis (Uni...
This position is for an Apple Subject Matter Expert to assist in developing the architecture, support and services for integration of Apple devices into the domain. Read more
*Apple* Macintosh OSX - Net2Source Inc. (Uni...
…: * Work Authorization : * Contact Number(Best time to reach you) : Skills : Apple Macintosh OSX Location : New York, New York. Duartion : 6+ Months The associate would Read more
Computer Operations Technician ll - *Apple*...
# Web Announcement** Apple Technical Liaison**The George Mason University, Information Technology Services (ITS), Technology Support Services, Desktop Support Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.