Ned to optimize the code

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November 30th, 2009, 01:30 PM
Mariusmssj

Ned to optimize the code

simple xox game but i kinda got a problem, that if statement works but it's too long, any ideas how to change into something better? and is there any better way to say the user won without having that "break;"?

thanks for any help =)

Code:

#include <iostream> #include <string> void main() { char grid[3][3] = {'.','.','.','.','.','.','.','.','.'}; int row = 0; int col = 0; char input; std::string msg = ""; std::cout<< " 0 1 2"<<"\n"<<"0 . . ."<<"\n"<<"1 . . ."<<"\n"<<"2 . . ."<<std::endl; for(int k=0;k<9;k++) { std::cout<< "Enter row: "; std::cin>> row; std::cout<< "Enter collum: "; std::cin>> col; std::cout<< "Enter X or O: "; std::cin>> input; grid[row][col]= input; for(int i=0;i<3;i++) { for(int j=0;j<3;j++) { std::cout<< grid[i][j]; } std::cout<< "\n"; } if(((((((((grid[0][0]=='x')&&(grid[0][1]=='x')&&(grid[0][2]=='x')|| (grid[1][0]=='x')&&(grid[1][1] == 'x')&&(grid[1][2]=='x')||(grid[2][0]=='x')&& (grid[2][1]=='x')&&(grid[1][2]=='x'))))))))) { msg = "you won"; break; } else { msg = "You lost"; } } std::cout<< msg; }

the output
http://img189.imageshack.us/img189/9720/outputk.jpg
November 30th, 2009, 01:51 PM
laserlight

Re: Ned to optimize the code

Quote:

Originally Posted by Mariusmssj

simple xox game but i kinda got a problem, that if statement works but it's too long, any ideas how to change into something better?

Move the expression into a function, then call that function in the if statement. It is not an optimisation, but a refactoring of code to make it more readable.
November 30th, 2009, 02:02 PM
treuss

Re: Ned to optimize the code

You can store the position of all X's in the lower 9 bits of an int (or a short if you want) by assigning each field a bit from 0-8. Likewise you can store the position of all O's in another int.

Using the same encoding, each three-in-a-row can be expressed as an int value, e.g. the value 7 represents the field 0, 1 and 2, 273 the fields 0, 4 and 8. Iterate over the list of all these values, and check for X's and O's if all bits of the value are set (use binary &). If they are, then the X's or O's have won.
November 30th, 2009, 02:13 PM
Mariusmssj

Re: Ned to optimize the code

Quote:

Originally Posted by laserlight

Move the expression into a function, then call that function in the if statement. It is not an optimisation, but a refactoring of code to make it more readable.

i got no idea about functions xD
November 30th, 2009, 02:21 PM
Mariusmssj

Re: Ned to optimize the code

Quote:

Originally Posted by treuss

You can store the position of all X's in the lower 9 bits of an int (or a short if you want) by assigning each field a bit from 0-8. Likewise you can store the position of all O's in another int.

Using the same encoding, each three-in-a-row can be expressed as an int value, e.g. the value 7 represents the field 0, 1 and 2, 273 the fields 0, 4 and 8. Iterate over the list of all these values, and check for X's and O's if all bits of the value are set (use binary &). If they are, then the X's or O's have won.

9 lower bits on an int?

so i would have int 1; and it would have some numbers which would be the directions on my 3 by 3 array grid?
November 30th, 2009, 02:26 PM
GCDEF

Re: Ned to optimize the code

Quote:

Originally Posted by Mariusmssj

i got no idea about functions xD

Now's a good time to learn. You can't program without them.

A nested if statement may be easier to read.

Code:

if(a) if(b) if(c) //..etc
November 30th, 2009, 02:37 PM
Mariusmssj

Re: Ned to optimize the code

Quote:

Originally Posted by GCDEF

Now's a good time to learn. You can't program without them.

A nested if statement may be easier to read.

Code:

if(a) if(b) if(c) //..etc

well i can't use functions because i will get marked down since the teacher haven't toughs us functions.

i read more about the nested if statements thank you ^_^
November 30th, 2009, 02:49 PM
Paul McKenzie

Re: Ned to optimize the code

Quote:

Originally Posted by Mariusmssj

9 lower bits on an int?

so i would have int 1; and it would have some numbers which would be the directions on my 3 by 3 array grid?

Number the board like this:

Code:

0 1 2 -----|------|----- 3 | 4 | 5 -----|------|----- 6 7 8

Each position on the board represents a bit in an integer. So if you have X's in 0,1,2, then bits 0, 1, and 2 of the integer are "on" (set to 1). The bits are numbered from right to left most, where bit 0 is the rightmost bit

000000111 == top row has all X's == 7

So 7 is a winning set of bits.

Another one is 0, 4, and 8 (the diagonal).

0100010001 = 273

Do the same with the other combinations, and you now have a list of integers that represent winning combinations.

Regards,

Paul McKenzie
November 30th, 2009, 02:52 PM
GCDEF

Re: Ned to optimize the code

Another way to improve readability would be to set values of several bools and just writ them in your if statement.

Code:

bool bGrid0 = grid[0][0] == 'x' && grid[0][1] == 'x'; bool bGrid1 = grid[1][0] == 'x' && grid[1][1] == 'x'; //etc. //then if(bGrid0 || bGrid1 || bGrid2) { //do stuff }

Get in the habit of using white space too. Not sure why beginners are so reluctant to put spaces between variable and operators.
November 30th, 2009, 02:56 PM
Paul McKenzie

Re: Ned to optimize the code

Quote:

Originally Posted by Mariusmssj

well i can't use functions because i will get marked down since the teacher haven't toughs us functions.

You asked how to "optimize" the code, and you can't really start optimizing until you learn to write functions to easily see what you should optimize.

Also, you have "void main()" instead of "int main()". The main() function returns an int, not void. So either your teacher is not teaching you C++ correctly and/or you're using books that are obsolete/out of date/wrong when it comes to teaching proper C++.

Regards,

Paul McKenzie
November 30th, 2009, 03:19 PM
Mariusmssj

Re: Ned to optimize the code

Quote:

Originally Posted by GCDEF

Another way to improve readability would be to set values of several bools and just writ them in your if statement.

Code:

bool bGrid0 = grid[0][0] == 'x' && grid[0][1] == 'x'; bool bGrid1 = grid[1][0] == 'x' && grid[1][1] == 'x'; //etc. //then if(bGrid0 || bGrid1 || bGrid2) { //do stuff }

Get in the habit of using white space too. Not sure why beginners are so reluctant to put spaces between variable and operators.

OMG it worked, THANKS i will need to read in more about the "bool"

Quote:

Originally Posted by Paul McKenzie

You asked how to "optimize" the code, and you can't really start optimizing until you learn to write functions to easily see what you should optimize.

Also, you have "void main()" instead of "int main()". The main() function returns an int, not void. So either your teacher is not teaching you C++ correctly and/or you're using books that are obsolete/out of date/wrong when it comes to teaching proper C++.

Regards,

Paul McKenzie

well he said he will teach us c then will advance further he wants us to know all the history not sure why though :S

but thank you for your help ^_^ what up to date websites could i use to learn c++?
December 1st, 2009, 05:46 AM
JohnW@Wessex

Re: Ned to optimize the code

This may help.

http://www.learncpp.com/

Quote:

well i can't use functions because i will get marked down since the teacher haven't taught us functions.

It make me sad to see students being marked down for showing some initiative.
December 1st, 2009, 05:53 AM
laserlight

Re: Ned to optimize the code

Quote:

Originally Posted by Mariusmssj

OMG it worked, THANKS i will need to read in more about the "bool"

hmm... won't you get marked down for using bool since your teacher has not taught you about that?
December 1st, 2009, 06:16 AM
Paul McKenzie

Re: Ned to optimize the code

Quote:

Originally Posted by laserlight

hmm... won't you get marked down for using bool since your teacher has not taught you about that?

I know, it can get really ridiculous as to what a teacher says can or can't be used. When I was a C++ teacher, I didn't care how a student solved the problem, as long as they can explain to me how they did it (even if what they did wasn't taught yet). If there is a general "you can't use this" construct, then it better be well-defined as to what can't be used.

Regards,

Paul McKenzie
December 1st, 2009, 08:06 AM
GCDEF

Re: Ned to optimize the code

If he's really learning C, bool shouldn't even compile.
December 1st, 2009, 02:26 PM
Mariusmssj

Re: Ned to optimize the code

Quote:

Originally Posted by JohnW@Wessex

This may help.

http://www.learncpp.com/

It make me sad to see students being marked down for showing some initiative.

thanks i just bookmarked it
well i am still going to learn about the functions before he actually will teach us it.

Quote:

Originally Posted by laserlight

hmm... won't you get marked down for using bool since your teacher has not taught you about that?

that is a really good point

Quote:

Originally Posted by Paul McKenzie

I know, it can get really ridiculous as to what a teacher says can or can't be used. When I was a C++ teacher, I didn't care how a student solved the problem, as long as they can explain to me how they did it (even if what they did wasn't taught yet). If there is a general "you can't use this" construct, then it better be well-defined as to what can't be used.

Regards,

Paul McKenzie

i will have to ask him that tomorrow, it;s really stupid of how it's being done

Quote:

Originally Posted by GCDEF

If he's really learning C, bool shouldn't even compile.

but it did xD and it works just fine

and i just want say thanks for all of you, and all the help you gave me ^_^
December 1st, 2009, 02:29 PM
ZuK

Re: Ned to optimize the code

Quote:

Originally Posted by GCDEF

If he's really learning C, bool shouldn't even compile.

It would compile if the compiler supports C99 and <stdbool.h> is #included

Kurt