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
} 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
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:

Latest Forum Discussions

Fresh From the Land Down Under – The Tou...
After a two week hiatus, we are back with another episode of The TouchArcade Show. Eli is fresh off his trip to Australia, which according to him is very similar to America but more upside down. Also kangaroos all over. Other topics this week... | Read more »
TouchArcade Game of the Week: ‘Dungeon T...
I’m a little conflicted on this week’s pick. Pretty much everyone knows the legend of Dungeon Raid, the match-3 RPG hybrid that took the world by storm way back in 2011. Everyone at the time was obsessed with it, but for whatever reason the... | Read more »
Hello gentle readers, and welcome to the SwitchArcade Round-Up for July 19th, 2024. In today’s article, we finish up the week with the unusual appearance of a review. I’ve spent my time with Hot Lap Racing, and I’m ready to give my verdict. After... | Read more »
Draknek Interview: Alan Hazelden on Thin...
Ever since I played my first release from Draknek & Friends years ago, I knew I wanted to sit down with Alan Hazelden and chat about the team, puzzle games, and much more. | Read more »
The Latest ‘Marvel Snap’ OTA Update Buff...
I don’t know about all of you, my fellow Marvel Snap (Free) players, but these days when I see a balance update I find myself clenching my… teeth and bracing for the impact to my decks. They’ve been pretty spicy of late, after all. How will the... | Read more »
‘Honkai Star Rail’ Version 2.4 “Finest D...
HoYoverse just announced the Honkai Star Rail (Free) version 2.4 “Finest Duel Under the Pristine Blue" update alongside a surprising collaboration. Honkai Star Rail 2.4 follows the 2.3 “Farewell, Penacony" update. Read about that here. | Read more »
‘Vampire Survivors+’ on Apple Arcade Wil...
Earlier this month, Apple revealed that poncle’s excellent Vampire Survivors+ () would be heading to Apple Arcade as a new App Store Great. I reached out to poncle to check in on the DLC for Vampire Survivors+ because only the first two DLCs were... | Read more »
Homerun Clash 2: Legends Derby opens for...
Since launching in 2018, Homerun Clash has performed admirably for HAEGIN, racking up 12 million players all eager to prove they could be the next baseball champions. Well, the title will soon be up for grabs again, as Homerun Clash 2: Legends... | Read more »
‘Neverness to Everness’ Is a Free To Pla...
Perfect World Games and Hotta Studio (Tower of Fantasy) announced a new free to play open world RPG in the form of Neverness to Everness a few days ago (via Gematsu). Neverness to Everness has an urban setting, and the two reveal trailers for it... | Read more »
Meditative Puzzler ‘Ouros’ Coming to iOS...
Ouros is a mediative puzzle game from developer Michael Kamm that launched on PC just a couple of months back, and today it has been revealed that the title is now heading to iOS and Android devices next month. Which is good news I say because this... | Read more »

Price Scanner via MacPrices.net

Amazon is still selling 16-inch MacBook Pros...
Prime Day in July is over, but Amazon is still selling 16-inch Apple MacBook Pros for \$500-\$600 off MSRP. Shipping is free. These are the lowest prices available this weekend for new 16″ Apple... Read more
Walmart continues to sell clearance 13-inch M...
Walmart continues to offer clearance, but new, Apple 13″ M1 MacBook Airs (8GB RAM, 256GB SSD) online for \$699, \$300 off original MSRP, in Space Gray, Silver, and Gold colors. These are new MacBooks... Read more
Apple is offering steep discounts, up to \$600...
Apple has standard-configuration 16″ M3 Max MacBook Pros available, Certified Refurbished, starting at \$2969 and ranging up to \$600 off MSRP. Each model features a new outer case, shipping is free,... Read more
Save up to \$480 with these 14-inch M3 Pro/M3...
Apple has 14″ M3 Pro and M3 Max MacBook Pros in stock today and available, Certified Refurbished, starting at \$1699 and ranging up to \$480 off MSRP. Each model features a new outer case, shipping is... Read more
Amazon has clearance 9th-generation WiFi iPad...
Amazon has Apple’s 9th generation 10.2″ WiFi iPads on sale for \$80-\$100 off MSRP, starting only \$249. Their prices are the lowest available for new iPads anywhere: – 10″ 64GB WiFi iPad (Space Gray or... Read more
Apple is offering a \$50 discount on 2nd-gener...
Apple has Certified Refurbished White and Midnight HomePods available for \$249, Certified Refurbished. That’s \$50 off MSRP and the lowest price currently available for a full-size Apple HomePod today... Read more
The latest MacBook Pro sale at Amazon: 16-inc...
Amazon is offering instant discounts on 16″ M3 Pro and 16″ M3 Max MacBook Pros ranging up to \$400 off MSRP as part of their early July 4th sale. Shipping is free. These are the lowest prices... Read more
14-inch M3 Pro MacBook Pros with 36GB of RAM...
B&H Photo has 14″ M3 Pro MacBook Pros with 36GB of RAM and 512GB or 1TB SSDs in stock today and on sale for \$200 off Apple’s MSRP, each including free 1-2 day shipping: – 14″ M3 Pro MacBook Pro (... Read more
14-inch M3 MacBook Pros with 16GB of RAM on s...
B&H Photo has 14″ M3 MacBook Pros with 16GB of RAM and 512GB or 1TB SSDs in stock today and on sale for \$150-\$200 off Apple’s MSRP, each including free 1-2 day shipping: – 14″ M3 MacBook Pro (... Read more
Amazon is offering \$170-\$200 discounts on new...
Amazon is offering a \$170-\$200 discount on every configuration and color of Apple’s M3-powered 15″ MacBook Airs. Prices start at \$1129 for models with 8GB of RAM and 256GB of storage: – 15″ M3... Read more

Jobs Board

*Apple* Systems Engineer - Chenega Corporati...
…LLC,** a **Chenega Professional Services** ' company, is looking for a ** Apple Systems Engineer** to support the Information Technology Operations and Maintenance Read more
Solutions Engineer - *Apple* - SHI (United...
**Job Summary** An Apple Solution Engineer's primary role is tosupport SHI customers in their efforts to select, deploy, and manage Apple operating systems and Read more
*Apple* / Mac Administrator - JAMF Pro - Ame...
Amentum is seeking an ** Apple / Mac Administrator - JAMF Pro** to provide support with the Apple Ecosystem to include hardware and software to join our team and Read more
Operations Associate - *Apple* Blossom Mall...
Operations Associate - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Read more
Cashier - *Apple* Blossom Mall - JCPenney (...
Cashier - Apple Blossom Mall Location:Winchester, VA, United States (https://jobs.jcp.com/jobs/location/191170/winchester-va-united-states) - Apple Blossom Mall Read more