Computer Science I
Looking at code: "Where did Prof. Shablinsky go?”
Reprise on Add to 15 implementation
Classwork/homework: Catch up: classy project.
Propose midterm project.
Feedback on error messages
While programming in Processing
• Some you can ignore because you haven’t gotten
to code something yet.
• BUT look at them because maybe the message
indicates a mistake.
• For example, methods (aka functions) are defined
to take specific arguments.
void calculate(float v, float w) {…} is not the same
as
void calculate(int v) { }
Feedback
• You need to zip the FOLDER, containing the .pde
file and, possibly, a data file, and, possibly, other
things…
• USE THE NAMING CONVENTION:
jMeyerBouncingThingsWClasses
• You may have problems in re-using names.
Download may produce
jMeyerBouncingThings (1).zip
which could produce folder NOT matching .pde
file name. Solution: erase old stuff or change
name.
Why classes
• Like functions and variables, classes are a way to
extend the language to [better] suit your
application.
• Bouncing things used classes so
– The same code used when possible
– Different code used when necessary. The different
code was defined in a structured way.
• Classes are not especially abstract. Think about
what are the entities (things) in your application?
– Look at the Slingshot sketch later in the class.
Class
• A class definition is the template for any number
of distinct objects.
• An object is set up using the new operator and
invoking the constructor. So if Thingee is the
name of a class
Thingee myThingee = new Thingee( );
Builds of object of datatype Thingee, setting values.
• The methods of the class can be invoked for each
object using dot notation. The variables can be
set or accessed using dot notation.
Arrays and Classes
• You can use one or both for your particular
project.
– Except sometimes I required one or the other for
an assignment!
• The Add to 15 has a more or less intricate use
of arrays
– Values in certain arrays are indices into other
arrays.
Feedback
• Consider use of array in place of
Box1, Box2, …
• Then you can use loops
for (int i<0;i<boxes.length;i++) {
…
}
• Do use distinct names for things that have specific roles
Thing badguy = new Thing(…);
Thing goodguy = new Thing(...);
Things[] stuffToDisplay = {badguy,goodguy,…}
Idea for game
• Display world map
• Player attempts to guess where Prof. Shablinsky went
during a summer a couple of years ago? Answers are:
– Iceland
– St. Petersberg
• While player is thinking, a shrinking image travels towards
mouse position. Elapsed time shown.
• If player clicks the screen, flyer appears where the mouse
was clicked. Two possibilities for message:
– Positive message
– Distance in pixels from closest of two answers
• If alloted time runs out,
– Time ran out
Processing features
• The background function can take an image as
an argument. This is how I make the map be
the background:
background(bg);
• The nf function formats floats. So if secs has
the value 5.100101, then
nf(secs,1,2); will produce the string "5.10"
Planning
• Manage two phases: inmotion Boolean
variable (aka flag)
• Define
– setup
– Draw
• If inmotion: move flyer image towards mouse
• Else: give response
– mouseClicked
– checkanswer
– giveresponse
Planning, cont.
• Move (animate) the flyer (the Irina image)
towards the mouse position.
• Animation stops at the end of a fixed time
duration set to 5 seconds OR if player clicks on
the map.
• If player clicks on the map, a computation is done
using the dist function to see if the player's
location is near enough to one of the answer.
Appropriate response given.
• If time runs out, a response is given.
Examine program
• Notice comments, including commented out code: used for
debugging.
• The world map displayed using
Pimage bg;
In setup: bg = loadImage(filename);
In draw: background(bg);
• The distance in pixels is calculated by builtin function dist. A forloop calculates what of the two places is closer and then compares
that number to 10, the tolerance allowed. This may be too strict.
• The function nf is used to format the elapsed time to display 2
decimal places.
• The flyer image dimensions are continuously changed, but kept in
proportion using wdel, fw, and fh variables.
fw -= wdel;
fh = fw*(origh/origw);
PImage bg;
PImage flyer;
boolean inmotion = true;
boolean clicked = false;
float duration = 5; // 5 seconds
float framer = 50;
float interval = 1/framer; //frame interval in time
float x,y,fw,fh,wdel;
float origw,origh,smallw;
PFont font;
String question = "Where did Professor Shablinsky travel this
summer?";
int[][] answers = {{452,90},{367,77}};
String[] answertexts = {"St. Petersberg, Russia", "Iceland"};
String responsetext;
Functions
•
•
•
•
•
setup
draw
mouseClicked
checkAnswer (float cx, float cy)
giveresponse
Reprise on Add to 15
• Rules of the game
• Implementation
– Prepare data ahead of time
• No addition to 15
– Example of use of arrays
• Arrays with pointers (indices) into other arrays
Starting position
After first moves
Finish of a game
Similar to
• … tic tac toe
• In fact, equivalent
– What does that mean?
• Examine game
Characteristics
• 9 moves
• What are winning combinations?
–951
–?
Number of combinations
• 8
• Same as number of rows + columns +
diagonals!!!
• Suggestion for the proof
– Assign the numbers to the 9 locations on the
tic tac toe grid to make valid combination in each
row, column and diagonal
– Try to do it
Here is a way
• For each number, count up presence in
winning combinations.
• 5 is present in 4, so….it goes in the middle.
• There are 4 numbers that are present in 3, so
they go in the corners,
– First placement is arbitrary….keep going.
My approach to smartmove
• Check for immediate win
• Check for immediate need to block
• Check for group with 1 computer move and no
player move
• Take the 5, if available
• Take a corner, if available
– Late addition. May not be needed
• Make random move
Implementation
• HTML, CSS, JavaScript
• Processing
– Continually re-drawing window AND checking for
mouse clicks
• Both implementations use arrays to hold the
information on winning combinations
– No adding up values
– Some use of place holder for first slot
[Some] variables
int[] player = {};
int[] computer = {};
int[] board = {1,2,3,4,5,6,7,8,9};
String[] groups = {
" ", //place holder, not used
"3 4 8", "1 5 9", "2 6 7", "1 6 8", "3 5 7", "2 4 9", "2 5 8", "4 5 6"
};
int[][] occupied = { //indexed subtracting 1
{2, 4},
{3, 6, 7},
{1, 5},
{1, 6, 8},
{2, 5, 7, 8},
{3, 4, 8},
{3, 5},
{1, 4, 7},
{2, 6}
};
int[] pgroupcount = {0,0,0,0,0,0,0,0,0}; //unused first slot
int[] cgroupcount = {0,0,0,0,0,0,0,0,0}; //unused first slot
Tracking progress
• The pgroupcount array indicates what the player has with respect
to each of the 8 possible winning combinations.
• So given winning combinations
String[] groups = {
" ", //place holder, not used
"3 4 8", "1 5 9", "2 6 7", "1 6 8", "3 5 7", "2 4 9", "2 5 8", "4 5 6"
};
If computer is {1,2,5} then cgroupcount will be
{0, 0, 2, 1, 1, 1, 1, 2, 1}
Computer wins if the 9 or the 8 is available to be taken, that is, still on
the board.
int smartChoice() {
//first check for immediate win
int boardl = board.length;
for (int i=0;i<boardl;i++) {
int possible = board[i];
for (int j=0;j<occupied[possible-1].length;j++) {
if (cgroupcount[occupied[possible-1][j]]==2) {
return (i);
}
}
}
….
General comments
• Repeat: My code never adds up numbers.
• Sometimes, let your program do the work,
and sometimes… no.
– Only 8 valid combinations.
– Keeping track of progress towards satisfying each
combination works.
• The human, even expert, approach may not
be the best approach for a program.
– Reference: chess programs.
Challenges
• Play game and design and implement a perfect strategy
for "the computer"
– Always wins or, at worse case, ties
• Make it possible for computer to start.
• Make computer skill adjustable (levels)
– Perhaps random, takes any win, my strategy, yours?
• Improve "look and feel" of game.
– Adding pause before computer move
• Add feature to keep record of moves.
• Add keeping score feature.
• ?
Classwork / Homework
• Catch up on classy project.
• Propose midterm project
– Wait for my approval and/or feedback.
• Study for midterm
– Check out midterm guide
– Prepare questions for second half of class