counting rows in a 2D array

This is a discussion on counting rows in a 2D array within the C Programming forums, part of the General Programming Boards category; Okay im a complete newbie when it comes to C. I need to write a function that takes a 2D ...

  1. #1
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    counting rows in a 2D array

    Okay im a complete newbie when it comes to C. I need to write a function that takes a 2D array as an input and then counts the number of rows in the 2D array. I have played around a bit and did some random testing but i keep hitting a wall(C not keeping track of array boundaries!). The general idea behind the code is simple and i just find it hard to believe something so simple is impossible to implement. HELP!

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    The arrays size, including it's number of rows, are fixed, when you create the array.

    You need to post some code, because what you're saying, doesn't agree with da C.

  3. #3
    msh
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    Code:
    size_t element_count = sizeof(array) / sizeof(*array);

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    Algorithm Dissector iMalc's Avatar
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    Please show us what you've tried.
    My homepage
    Advice: Take only as directed - If symptoms persist, please see your debugger

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    Quote Originally Posted by msh View Post
    Code:
    size_t element_count = sizeof(array) / sizeof(*array);
    But he's asking for the number of rows, instead of elements.

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    msh
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    Quote Originally Posted by Adak View Post
    But he's asking for the number of rows, instead of elements.
    Ambiguous variable naming on my part. In an array of arrays (rows), rows are the elements. At least that's how I understand it.

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    True ^^^, but the OP specified a 2D array.

    Wriggle room is very limited here!

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    msh
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    Quote Originally Posted by Adak View Post
    True ^^^, but the OP specified a 2D array.

    Wriggle room is very limited here!
    Fair enough. But now I can't edit because you already quoted it.

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    Angry

    alright thanks guys for the quick response. Below is some code iv'e tried.

    char str[3][3] ={"1","2","3"};
    int i = 0;
    while(str[i] != NULL || *str[i] = '\0')
    {
    i++
    }

    this however doesn't work at all. As apparently the out of boundary areas posses values.
    Help?

  10. #10
    msh
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    Code for what you want was already posted; read the bloody thread.

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    Oh!.... Sorry there!
    I couldn't tell if what you posted, was exactly what you wanted( you stated that you couldn't edit it?).
    either way thanks a lot!
    Testing it out right now.
    Last edited by Kyoukoku; 09-22-2010 at 08:10 AM.

  12. #12
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    Quote Originally Posted by Kyoukoku View Post
    alright thanks guys for the quick response. Below is some code iv'e tried.

    char str[3][3] ={"1","2","3"};
    int i = 0;
    while(str[i] != NULL || *str[i] = '\0')
    {
    i++
    }

    this however doesn't work at all. As apparently the out of boundary areas posses values.
    Help?
    Use code tags [code][/code] when posting code samples.

    str[i] will never be null since (in this context) it is an address that always exists regardless of how many actual elements exist. If str[0] exists at address 1000 and str[1] exists at 1003 and str[2] exists at 1006, then str[3] exists at 1009 regardless of whether there is a str[3] at all. This is because of simple pointer arithmetic. An example (granted this one is C++) would easily show this:
    Code:
        char str[3][3] = {"1","2","3"};
    
        for( int i = 0; i < 5; ++i )
        {
            std::cout << "str[" << i << "] is : " << str[i];
            std::cout << " the address is: " << reinterpret_cast<void*>(str[i]) << std::endl;
        }
    Output is below, of note just look at the address listed. It simply increases by 3 even though the elements beyond str[2] do not exist.
    Attached Images Attached Images  
    Last edited by hk_mp5kpdw; 09-22-2010 at 08:32 AM. Reason: Can't count 1,2,4?
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  13. #13
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    Code:
    char str[3][3] ={"1","2","3"};
    int i = 0;
    while(str[i] != NULL || *str[i] = '\0')
    {
    i++
    }
    I wonder
    char str[3][3]


    if you
    char str[3][3]


    could tell me
    char str[3][3]


    how many
    char str[3][3]


    rows are in
    char str[3][3]


    my char array?

    char str[3][3]


    Help?

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