Thread: Vector of Vectors

  1. #1
    Registered User
    Join Date
    Sep 2005

    Vector of Vectors


    I need to know how to declare a vector of vectors and how to access.

    vector <int> int_vec;
    #need a vector containing vectors.

    Then I need to do
    vector_Containing vectors.push_back(int_vec);
    clear int_vec for use again

    Also, how do I reference the integer now
    ie The integer in container vector position 0 and integer vector position 1.


  2. #2
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  3. #3
    Moderately Rabid Decrypt's Avatar
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    You know the syntax for declaring a vector of int, a vector of vectors of int is only a small step.

    The syntax for declaring a vector is
    vector<data_type> vector_name;
    So, in your case, you want a vector of vectors of int. So put vector<int> in for data_type, and we get
    vector<vector<int> > vector_name;
    In general, the rule on whitespace in your code is that it's ignored, that is:
    cout << someVar;
    cout<<                           someVar;
    are all the same. In the above declaration, the space between the two greater-than signs is neccessary. The compiler will be confused thinking you're using the insertion operator. That doesn't sound so clear re-reading it, so as an example:
    vector<vector<int> > vecName;       //this is good
    vector<vector<int>> vecName;        //BAD swanley!  NAUGHTY! {swats you on the nose with a newspaper}
    As far as pushing elements onto the vectors and accessing elements in a vector of vectors, do some more research. Try to see if you can get it on your own, and if not, post what you've tried and why you think it's not working.
    There is a difference between tedious and difficult.

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