Array Problems? (Im a beginner)

scarlet00014 · 09-19-2008, 02:19 PM

Code:

 
array[x][y];

Ok Im able to read in a double array of numbers, and print them out just fine with this code:

Code:

    for (i=0; i<x; i++){
        for(j=0; j<y; j++){
                array[i][j] = array[i][j];
                printf("%d\n", array[i][j]);
            }

        j=0;
    }

But when I try to flip the array horizontally, it doesnt work.. this is the code i use:

Code:

    for (i=0; i<x; i++){
        for(j=y-1; j>0; j--){
                array[i][j] = array[i][j];
                printf("%d\n", array[i][j]);
            }

        j=y-1;
    }

what should i do to make it flip horizontally?

master5001 · 09-19-2008, 02:24 PM

I am adding some variables to your code and assuming some things about what you are wanting to do.

Code:

    for (i=0; i<x; i++){
        for(j=y-1, k = 0; j>=0; j--, k++){
                temp = array[i][j];
                array[i][j] = array[i][k];
                array[i][k] = temp;
                printf("%d\n", array[i][j]);
            }
    }

master5001 · 09-19-2008, 02:25 PM

I should have probably asked... What do you mean by flip them horizontally? Like reverse them along the y-axis?

matsp · 09-19-2008, 02:26 PM

Code:

array[i][j] = array[i][j];

this line does absolutely nothing (it moves to and from the same place in the array).

Your line that sets "j = ..." in both of your code-samples is also meaningless.

I'm not sure what you meany "not working", as your code seems to be correct.

--
Mats

scarlet00014 · 09-19-2008, 02:41 PM

Quote:

Originally Posted by master5001

I should have probably asked... What do you mean by flip them horizontally? Like reverse them along the y-axis?

yes along the y axis..

so :

1 2 3
4 5 6

would be

3 2 1
6 5 4

master5001 · 09-19-2008, 02:52 PM

Ok well the code I posted does that.

matsp · 09-19-2008, 02:54 PM

So, do you just want to print them back to front, or change the content around so that the content is stored the other way around?

If the latter, then master5001 has answered this (you need a temporary variable to store the value when swapping the locations). Although I think you should only iterate over half of the content, as otherwise you'd end up swapping everything back again.

--
Mats

scarlet00014 · 09-19-2008, 02:57 PM

its working now..

it needed to be

j >= 0;

ugh duh

master5001 · 09-19-2008, 02:59 PM

Yeah I bolded that part, I wasn't sure if it was noticeable to you. I usually put it in red, but that was not the only problem that I spotted..

09-19-2008, 02:19 PM	#1
scarlet00014 Registered User Join Date: Sep 2008 Posts: 58	Array Problems? (Im a beginner) Code: array[x][y]; Ok Im able to read in a double array of numbers, and print them out just fine with this code: Code: for (i=0; i<x; i++){ for(j=0; j<y; j++){ array[i][j] = array[i][j]; printf("%d\n", array[i][j]); } j=0; } But when I try to flip the array horizontally, it doesnt work.. this is the code i use: Code: for (i=0; i<x; i++){ for(j=y-1; j>0; j--){ array[i][j] = array[i][j]; printf("%d\n", array[i][j]); } j=y-1; } what should i do to make it flip horizontally?
scarlet00014 is offline

09-19-2008, 02:24 PM	#2
master5001 Banned Join Date: Aug 2001 Location: Visalia, CA, USA Posts: 3,699	I am adding some variables to your code and assuming some things about what you are wanting to do. Code: for (i=0; i<x; i++){ for(j=y-1, k = 0; j>=0; j--, k++){ temp = array[i][j]; array[i][j] = array[i][k]; array[i][k] = temp; printf("%d\n", array[i][j]); } } Last edited by master5001; 09-19-2008 at 02:29 PM.
master5001 is offline

09-19-2008, 02:25 PM	#3
master5001 Banned Join Date: Aug 2001 Location: Visalia, CA, USA Posts: 3,699	I should have probably asked... What do you mean by flip them horizontally? Like reverse them along the y-axis?
master5001 is offline

09-19-2008, 02:26 PM	#4
matsp Kernel hacker Join Date: Jul 2007 Location: Farncombe, Surrey, England Posts: 15,686	Code: array[i][j] = array[i][j]; this line does absolutely nothing (it moves to and from the same place in the array). Your line that sets "j = ..." in both of your code-samples is also meaningless. I'm not sure what you meany "not working", as your code seems to be correct. -- Mats __________________ Compilers can produce warnings - make the compiler programmers happy: Use them! Please don't PM me for help - and no, I don't do help over instant messengers.
matsp is offline

09-19-2008, 02:52 PM	#6
master5001 Banned Join Date: Aug 2001 Location: Visalia, CA, USA Posts: 3,699	Ok well the code I posted does that.
master5001 is offline

09-19-2008, 02:54 PM	#7
matsp Kernel hacker Join Date: Jul 2007 Location: Farncombe, Surrey, England Posts: 15,686	So, do you just want to print them back to front, or change the content around so that the content is stored the other way around? If the latter, then master5001 has answered this (you need a temporary variable to store the value when swapping the locations). Although I think you should only iterate over half of the content, as otherwise you'd end up swapping everything back again. -- Mats __________________ Compilers can produce warnings - make the compiler programmers happy: Use them! Please don't PM me for help - and no, I don't do help over instant messengers.
matsp is offline

09-19-2008, 02:57 PM	#8
scarlet00014 Registered User Join Date: Sep 2008 Posts: 58	its working now.. it needed to be j >= 0; ugh duh
scarlet00014 is offline

09-19-2008, 02:59 PM	#9
master5001 Banned Join Date: Aug 2001 Location: Visalia, CA, USA Posts: 3,699	Yeah I bolded that part, I wasn't sure if it was noticeable to you. I usually put it in red, but that was not the only problem that I spotted..
master5001 is offline

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