2D array output help

This is a discussion on 2D array output help within the C++ Programming forums, part of the General Programming Boards category; Hi, I am new to C++ and in need of a little help. I am trying to output a two ...

  1. #1
    Unregistered
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    2D array output help

    Hi, I am new to C++ and in need of a little help.

    I am trying to output a two dimension array of student names, "n[][30]". The names that are being inputed are: Corey, David, Kacey, Terry

    The code I have at the moment is:

    #define STUDENTCOUNT 4
    .
    .
    .
    .

    cout << "Name" << endl;
    for(int i = 0; i < STUDENTCOUNT; i++)
    {
    cout << n[i][30] << " \n";
    }
    The output that I get is

    Name
    D
    K
    T
    8

    Any ideas on why I am getting this output would be appreciated.

  2. #2
    Registered User
    Join Date
    Mar 2002
    Posts
    13
    Basicallly you are only outputting one character of each of the names and not all of them.

    n[i][30] only points to one character (the 30th) in each of names. And as the names dont fill up all the 30 allocated characters the empty spaces contain garbage. Thats why you are getting the 8 printed.


    To remedy you would create another for loop that seqeunces through the 30 characters in each element.

    eg.

    for(int i = 0; i < STUDENTCOUNT; i++)
    {
    for(int j = 0; j < 30; j++)
    {
    cout << n[i][j];
    }
    count << "/n";
    }

  3. #3
    Unregistered
    Guest
    Thanks for that help, now it will print the whole name, but it's also printing garbage in between the names.

    I tried playing with the /n escape sequence, but all I got were the names one character per line, and garbage in between

    How would I get to the next line after I input a name thats less than the 30 allocated spaces, without getting all that extra garbage in between.

    Right now im getting

    Name
    Corey[|[|[|[|[|[|David[|[|[|[|[|[|Kacey[|[|[|[|[|[|[|[|[|Terry

    the output should be
    Name:
    Corey
    David
    Kacey
    Terry

  4. #4
    Registered User
    Join Date
    Mar 2002
    Posts
    203
    you should be able to display the name entirely instead of character by character, just drop off the second dimention.

    for(int i = 0; i < STUDENTCOUNT; i++)
    {
    cout << n[i] << " \n";
    }

    ofcourse each string needs to be null terminated, but depending on how you input the name they already are
    this method works because of the relationship between character arrays and pointers I haven't felt like bothering with the non-basic complexities of pointers yet, so if someone would like to explain exactly how this work then feel free

  5. #5
    Unregistered
    Guest
    AH HA!

    That got it working. Thanks for the help guys, it is truly appreciated.

    Being a newbie, truly sucks.

    So if I am understanding correctly, since the inputing of the names was null terminated upon entering them, the second dimension is not needed for the outputing.

    Hence the unused character spaces were represented as garbage.

  6. #6
    Registered User
    Join Date
    Mar 2002
    Posts
    203
    actually i think it has more to do with pointers, but all character arrays(strings) should be null terminated. the null character (\0) is very useful because it marks the end of a string.
    I can't explain it too well because i'm still a newbie myself, well more like a newbie lvl 2 i think next i'll learn more about pointers and pointer notation. I'm sure it'll help with classes.

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