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Thread: Number of elements in a list of list

  1. #1
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    Default Number of elements in a list of list

    Hello everyone, I have a problem like this: I do not know how to count the number of elements in a list of lists. Let me explain:
    I have the following list of list
    Qt Code:
    1. std::vector< std::vector<GLdouble> > contours;
    2. ...
    3. std::vector< std::vector<GLdouble> >::iterator contour;
    4. for(contours.begin(), ite = contours.end(); contour != ite; ++contour)
    5. {
    6. for( size_t v = 0; v < ????; v += 3 )
    7. }
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    I do not know how to write the part indicated with ???? that represents the size (ie the number of elements of the list std::vector<GLdouble>).
    Can you help me, I'm going crazy.

  2. #2
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    Default Re: Number of elements in a list of list

    Qt Code:
    1. vector<vector<int>> lotsOfInts;
    2. // ...
    3. size_t outerVectorSize = lotsOfInts.size();
    4. size_t firstInnerVectorSize = lotsOfInts.begin()->size();
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    hope you can figure it out from that.

    This is trivial c++ and definitely not Qt programming specific. Please consider better which forum you ask these questions in.
    If you have a problem, CUT and PASTE your code. Do not retype or simplify it. Give a COMPLETE and COMPILABLE example of your problem. Otherwise we are all guessing the problem from a fabrication where relevant details are often missing.

  3. #3
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    Default Re: Number of elements in a list of list

    thanks amleto

  4. #4
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    Default Re: Number of elements in a list of list

    KO, not good. those are the elements of contour at each iteration ?

  5. #5
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    Default Re: Number of elements in a list of list

    please get acquainted with online references. Here is a good start:
    http://www.cplusplus.com/reference/vector/vector/

    This is not a forum to teach c++ to beginners.
    If you have a problem, CUT and PASTE your code. Do not retype or simplify it. Give a COMPLETE and COMPILABLE example of your problem. Otherwise we are all guessing the problem from a fabrication where relevant details are often missing.

  6. #6
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    Default Re: Number of elements in a list of list

    This tips seems quite interesting and good to me.

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