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How to Get Length Of Int* Array

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  • J.HilkJ J.Hilk

    @Ketan__Patel__0011
    you need to either reserve a size for your vectors or use the vector functions to append data

    push_back, resize, reserve etc

    https://en.cppreference.com/w/cpp/container/vector

    or use initializer lists

    Ketan__Patel__0011K Offline
    Ketan__Patel__0011K Offline
    Ketan__Patel__0011
    wrote on last edited by
    #11

    @J-Hilk

    I was Try this But Application is Still Crashing

    	std::vector<std::vector<std::vector<int>>> Temp;
    
    	Temp.at(0).at(0).push_back(10);
    	Temp.at(0).at(0).push_back(20);
    	Temp.at(0).at(0).push_back(30);
    	Temp.at(0).at(0).push_back(40);
    
    	cout << Temp.at(0).at(0).at(0);
    	cout << Temp.at(0).at(0).at(1);
    	cout << Temp.at(0).at(0).at(2);
    	cout << Temp.at(0).at(0).at(3);
    
    
    J.HilkJ KroMignonK 2 Replies Last reply
    0
    • Ketan__Patel__0011K Ketan__Patel__0011

      @J-Hilk

      I was Try this But Application is Still Crashing

      	std::vector<std::vector<std::vector<int>>> Temp;
      
      	Temp.at(0).at(0).push_back(10);
      	Temp.at(0).at(0).push_back(20);
      	Temp.at(0).at(0).push_back(30);
      	Temp.at(0).at(0).push_back(40);
      
      	cout << Temp.at(0).at(0).at(0);
      	cout << Temp.at(0).at(0).at(1);
      	cout << Temp.at(0).at(0).at(2);
      	cout << Temp.at(0).at(0).at(3);
      
      
      J.HilkJ Offline
      J.HilkJ Offline
      J.Hilk
      Moderators
      wrote on last edited by J.Hilk
      #12

      @Ketan__Patel__0011

          std::vector<std::vector<std::vector<int>>> Temp;
      
          int targetSize = 4;
          Temp.resize(targetSize,std::vector<std::vector<int> >(targetSize,std::vector<int>(targetSize)));
      
          Temp.at(0).at(0).at(0) = 10;
          Temp.at(0).at(0).at(1) = 20;
          Temp.at(0).at(0).at(2) = 30;
          Temp.at(0).at(0).at(3) = 40;
      

      Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


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      A: It turns blue.

      1 Reply Last reply
      3
      • Ketan__Patel__0011K Ketan__Patel__0011

        @J-Hilk

        I was Try this But Application is Still Crashing

        	std::vector<std::vector<std::vector<int>>> Temp;
        
        	Temp.at(0).at(0).push_back(10);
        	Temp.at(0).at(0).push_back(20);
        	Temp.at(0).at(0).push_back(30);
        	Temp.at(0).at(0).push_back(40);
        
        	cout << Temp.at(0).at(0).at(0);
        	cout << Temp.at(0).at(0).at(1);
        	cout << Temp.at(0).at(0).at(2);
        	cout << Temp.at(0).at(0).at(3);
        
        
        KroMignonK Offline
        KroMignonK Offline
        KroMignon
        wrote on last edited by KroMignon
        #13

        @Ketan__Patel__0011 said in How to Get Length Of Int* Array:

        was Try this But Application is Still Crashing

        	std::vector<std::vector<std::vector<int>>> Temp;
        
        	Temp.at(0).at(0).push_back(10);
        

        Yes of course, the 2 first vector are not defined!

        You could read this article to learn how to work with multidimensionalvectors => https://mklimenko.github.io/english/2019/08/17/multidimensional-vector-allocation/

        It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

        1 Reply Last reply
        2
        • A Offline
          A Offline
          Asperamanca
          wrote on last edited by
          #14

          Maybe something like this helps:
          https://www.learncpp.com/cpp-tutorial/an-introduction-to-stdvector/

          It also refers to std::array, which might be an alternative if you really only need fixed-sized arrays.

          Ketan__Patel__0011K 1 Reply Last reply
          1
          • Ketan__Patel__0011K Offline
            Ketan__Patel__0011K Offline
            Ketan__Patel__0011
            wrote on last edited by Ketan__Patel__0011
            #15

            Thanks to All for your reply

            i can't find the length of the Vector

            KroMignonK 1 Reply Last reply
            0
            • Ketan__Patel__0011K Ketan__Patel__0011

              Thanks to All for your reply

              i can't find the length of the Vector

              KroMignonK Offline
              KroMignonK Offline
              KroMignon
              wrote on last edited by
              #16

              @Ketan__Patel__0011 have you really searched ? ==> https://www.cplusplus.com/reference/vector/vector/size/

              It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

              Ketan__Patel__0011K 1 Reply Last reply
              0
              • A Asperamanca

                Maybe something like this helps:
                https://www.learncpp.com/cpp-tutorial/an-introduction-to-stdvector/

                It also refers to std::array, which might be an alternative if you really only need fixed-sized arrays.

                Ketan__Patel__0011K Offline
                Ketan__Patel__0011K Offline
                Ketan__Patel__0011
                wrote on last edited by
                #17

                @Asperamanca
                thanks for your reply

                But Fixed Sized array not useful in my case

                1 Reply Last reply
                0
                • KroMignonK KroMignon

                  @Ketan__Patel__0011 have you really searched ? ==> https://www.cplusplus.com/reference/vector/vector/size/

                  Ketan__Patel__0011K Offline
                  Ketan__Patel__0011K Offline
                  Ketan__Patel__0011
                  wrote on last edited by
                  #18

                  @KroMignon

                  Yes i see this example

                  They Are Declare Singla Dimension Vector and Add First 10 Element and Again Add 10 Element After the First 10th Element Index and in last step they are remove the element and display the size of vector not a length

                  KroMignonK 1 Reply Last reply
                  0
                  • Ketan__Patel__0011K Ketan__Patel__0011

                    @KroMignon

                    Yes i see this example

                    They Are Declare Singla Dimension Vector and Add First 10 Element and Again Add 10 Element After the First 10th Element Index and in last step they are remove the element and display the size of vector not a length

                    KroMignonK Offline
                    KroMignonK Offline
                    KroMignon
                    wrote on last edited by
                    #19

                    @Ketan__Patel__0011 said in How to Get Length Of Int* Array:

                    display the size of vector not a length

                    I don't understand what you want?!?
                    By simply reading std::vector() documentation, you could find yourself:

                    • vector::size(): Returns the number of elements in the vector.
                    • vector::capacity(): Returns the size of the storage space currently allocated for the vector, expressed in terms of elements.

                    It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                    Ketan__Patel__0011K 1 Reply Last reply
                    0
                    • KroMignonK KroMignon

                      @Ketan__Patel__0011 said in How to Get Length Of Int* Array:

                      display the size of vector not a length

                      I don't understand what you want?!?
                      By simply reading std::vector() documentation, you could find yourself:

                      • vector::size(): Returns the number of elements in the vector.
                      • vector::capacity(): Returns the size of the storage space currently allocated for the vector, expressed in terms of elements.
                      Ketan__Patel__0011K Offline
                      Ketan__Patel__0011K Offline
                      Ketan__Patel__0011
                      wrote on last edited by
                      #20

                      @KroMignon

                      i want to find how many elements are in the My Vector

                      i was used vector::size() function but it is return to me total size of vector

                      for example

                      my Vector can store 10 elements but i am add only 6 elements

                      so my Vector length is 6 And Vector size is 10

                      KroMignonK Christian EhrlicherC 2 Replies Last reply
                      0
                      • Ketan__Patel__0011K Ketan__Patel__0011

                        @KroMignon

                        i want to find how many elements are in the My Vector

                        i was used vector::size() function but it is return to me total size of vector

                        for example

                        my Vector can store 10 elements but i am add only 6 elements

                        so my Vector length is 6 And Vector size is 10

                        KroMignonK Offline
                        KroMignonK Offline
                        KroMignon
                        wrote on last edited by
                        #21

                        @Ketan__Patel__0011 said in How to Get Length Of Int* Array:

                        i want to find how many elements are in the My Vector

                        Here are a little code extract which should be self explaining:

                           std::vector<int> test;
                            qDebug() << "Size is" << test.size() << "/ Capacity is" << test.capacity();
                            test.reserve(10);
                            qDebug() << "Size is" << test.size() << "/ Capacity is" << test.capacity();
                            test.push_back(11);
                            qDebug() << "Size is" << test.size() << "/ Capacity is" << test.capacity();
                            test.push_back(11);
                            test.push_back(11);
                            qDebug() << "Size is" << test.size() << "/ Capacity is" << test.capacity();
                            test.pop_back();
                            qDebug() << "Size is" << test.size() << "/ Capacity is" << test.capacity();
                        

                        and output is:
                        Size is 0 / Capacity is 0
                        Size is 0 / Capacity is 10
                        Size is 1 / Capacity is 10
                        Size is 3 / Capacity is 10
                        Size is 2 / Capacity is 10

                        It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                        1 Reply Last reply
                        4
                        • Ketan__Patel__0011K Ketan__Patel__0011

                          @KroMignon

                          i want to find how many elements are in the My Vector

                          i was used vector::size() function but it is return to me total size of vector

                          for example

                          my Vector can store 10 elements but i am add only 6 elements

                          so my Vector length is 6 And Vector size is 10

                          Christian EhrlicherC Offline
                          Christian EhrlicherC Offline
                          Christian Ehrlicher
                          Lifetime Qt Champion
                          wrote on last edited by
                          #22

                          @Ketan__Patel__0011 said in How to Get Length Of Int* Array:

                          so my Vector length is 6 And Vector size is 10

                          No, thats wrong. The size is 6, the std::vector<> has no function length().

                          Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
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                          1 Reply Last reply
                          4
                          • Kent-DorfmanK Offline
                            Kent-DorfmanK Offline
                            Kent-Dorfman
                            wrote on last edited by Kent-Dorfman
                            #23
                            This post is deleted!
                            1 Reply Last reply
                            0
                            • Kent-DorfmanK Offline
                              Kent-DorfmanK Offline
                              Kent-Dorfman
                              wrote on last edited by
                              #24

                              "length" of a multidimensional array is kind of a meaningless concept...and resizing those structures requires well defined conops of what it means to resize, and what to do with new elements, or elements that must be thrown away...AND...will almost always require complete data move to a new container of appropriate size.

                              While sometimes useful, a vector of vectors is nontrivial to manage correctly.

                              1 Reply Last reply
                              0
                              • JonBJ Offline
                                JonBJ Offline
                                JonB
                                wrote on last edited by JonB
                                #25

                                @Ketan__Patel__0011
                                I don't really understand just which "sizes" or "lengths" you are wanting to discover.

                                A vector of vectors is a jagged array, meaning that each sub-vector element in a parent vector has its own size/length/number of elements. It is not "rectangular" like C/C++ int array[outer_elements][inner_elements] would be. Also, unlike the C one, you can & do add elements at all levels dynamically, so the number of items change at runtime. You would have to iterate the vector to discover its child element sizes to discover the total size used. You can resize() and/or reserve() if you want to reserve a certain size (number of elements)/make it "rectangular", and thereby avoid needing to iterate to discover size if desired.

                                @Christian-Ehrlicher , @KroMignon , @J-Hilk have given you code/references for the above.

                                1 Reply Last reply
                                4
                                • X Offline
                                  X Offline
                                  xtofl
                                  wrote on last edited by xtofl
                                  #26

                                  vector will solve allocation/deallocation while keeping contiguous storage. It is intended for 1D arrays; everything more dimensional needs to come from somewhere else; doing it yourself while not familiar with C++ is probably not the best idea.

                                  Since it seems you're dealing with matrices, getting a dedicated, fast, reliable library is probably the best thing to do. I suggest looking into Eigen.

                                  1 Reply Last reply
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