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  4. How to remove elements from QStringList by comparing each other members.
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How to remove elements from QStringList by comparing each other members.

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  • VRoninV Offline
    VRoninV Offline
    VRonin
    wrote on last edited by
    #2

    What if files Test2 and Test5 are identical and the others are unique?
    do you want to compare just adiecent files in the list?

    "La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
    ~Napoleon Bonaparte

    On a crusade to banish setIndexWidget() from the holy land of Qt

    1 Reply Last reply
    0
    • A Offline
      A Offline
      Ayush Gupta
      wrote on last edited by
      #3

      I need to compare each file in list with another and remove the file if file has same contents and doing string comparison the name of the file which is less should be deleted.

      1 Reply Last reply
      0
      • A Offline
        A Offline
        Ayush Gupta
        wrote on last edited by
        #4

        @VRonin Can you help regardin this?

        mrjjM 1 Reply Last reply
        0
        • A Ayush Gupta

          @VRonin Can you help regardin this?

          mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by mrjj
          #5

          @Ayush-Gupta

          Hi
          How big are each file ?
          Can they all fit in memory at same time?

          What is the data inside ?

          Often one can use a checksum
          to see if files are the same but it depends on the data as
          sometimes a sequence of letters can have the same
          checksum as another even we logically would say they are not the same.

          1 Reply Last reply
          1
          • A Offline
            A Offline
            Ayush Gupta
            wrote on last edited by
            #6

            @mrjj
            I have the code to check if file are same or not.
            My problem is I am able to filter name from QStringList. I tried index also.
            Suppose there are 6 files in list and I need to compare each file ( for that I have code) which will do the thing.
            Then I need to compare the file name if fileName1 > fileName2 then delete fileName2 from list if comparison is equal.

            jsulmJ 1 Reply Last reply
            0
            • A Ayush Gupta

              @mrjj
              I have the code to check if file are same or not.
              My problem is I am able to filter name from QStringList. I tried index also.
              Suppose there are 6 files in list and I need to compare each file ( for that I have code) which will do the thing.
              Then I need to compare the file name if fileName1 > fileName2 then delete fileName2 from list if comparison is equal.

              jsulmJ Offline
              jsulmJ Offline
              jsulm
              Lifetime Qt Champion
              wrote on last edited by
              #7

              @Ayush-Gupta https://doc.qt.io/qt-5/qlist.html#erase

              https://forum.qt.io/topic/113070/qt-code-of-conduct

              1 Reply Last reply
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              • mrjjM Offline
                mrjjM Offline
                mrjj
                Lifetime Qt Champion
                wrote on last edited by
                #8

                Hi
                so if
                fileName1 and fileName2
                is the same.
                You must delete the file with the highest number in its name ?

                A 1 Reply Last reply
                0
                • mrjjM mrjj

                  Hi
                  so if
                  fileName1 and fileName2
                  is the same.
                  You must delete the file with the highest number in its name ?

                  A Offline
                  A Offline
                  Ayush Gupta
                  wrote on last edited by
                  #9

                  @mrjj yes

                  mrjjM 1 Reply Last reply
                  0
                  • A Ayush Gupta

                    @mrjj yes

                    mrjjM Offline
                    mrjjM Offline
                    mrjj
                    Lifetime Qt Champion
                    wrote on last edited by
                    #10

                    @Ayush-Gupta

                    Do you only have files 1 to max 9?

                        QString filename1 = "somename1";
                        QString filename2 = "somename2";
                    
                         int fno1=filename1.right(1).toInt();
                         int fno2=filename2.right(1).toInt();
                         
                         if (fno1 < fno2 ) ....
                    
                    

                    else you need better extraction.

                    1 Reply Last reply
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                    • VRoninV Offline
                      VRoninV Offline
                      VRonin
                      wrote on last edited by VRonin
                      #11

                      Something like this?

                      // QVector<QFile> fileList;
                      // bool equalFiles(const QFile&,const QFile&);
                      bool foundI;
                      for(auto i=fileList.begin(), maxJ = fileList.end(), maxI=maxJ-1;i!=maxI;){
                          foundI=false;
                          for(auto j=i+1;j!=maxJ && !foundI;){
                              if(equalFiles(*i,*j)){
                                  if(i->fileName()>j->fileName())
                                      j = fileList.erase(j);
                                  else
                                      foundI=true;
                              }
                              else
                                  ++j;
                          }
                          if(foundI)
                              i=fileList.erase(i);
                          else
                              ++i;
                      }
                      
                      

                      "La mort n'est rien, mais vivre vaincu et sans gloire, c'est mourir tous les jours"
                      ~Napoleon Bonaparte

                      On a crusade to banish setIndexWidget() from the holy land of Qt

                      Chris KawaC 1 Reply Last reply
                      0
                      • VRoninV VRonin

                        Something like this?

                        // QVector<QFile> fileList;
                        // bool equalFiles(const QFile&,const QFile&);
                        bool foundI;
                        for(auto i=fileList.begin(), maxJ = fileList.end(), maxI=maxJ-1;i!=maxI;){
                            foundI=false;
                            for(auto j=i+1;j!=maxJ && !foundI;){
                                if(equalFiles(*i,*j)){
                                    if(i->fileName()>j->fileName())
                                        j = fileList.erase(j);
                                    else
                                        foundI=true;
                                }
                                else
                                    ++j;
                            }
                            if(foundI)
                                i=fileList.erase(i);
                            else
                                ++i;
                        }
                        
                        
                        Chris KawaC Online
                        Chris KawaC Online
                        Chris Kawa
                        Lifetime Qt Champion
                        wrote on last edited by
                        #12

                        @VRonin That's a brute force N! complexity algorithm on file contents. That's horrible.

                        @Ayush-Gupta Create a [hash]->[filename] map. Read each file in sorted order and calculate their hash (MD5, SHA-1 or whatever works for you). Put the file name in the map using that hash and your resulting map will contain all the filenames with unique contents.

                        Christian EhrlicherC 1 Reply Last reply
                        4
                        • Chris KawaC Chris Kawa

                          @VRonin That's a brute force N! complexity algorithm on file contents. That's horrible.

                          @Ayush-Gupta Create a [hash]->[filename] map. Read each file in sorted order and calculate their hash (MD5, SHA-1 or whatever works for you). Put the file name in the map using that hash and your resulting map will contain all the filenames with unique contents.

                          Christian EhrlicherC Offline
                          Christian EhrlicherC Offline
                          Christian Ehrlicher
                          Lifetime Qt Champion
                          wrote on last edited by
                          #13

                          @Chris-Kawa Before creating the hash I would compare the filesize (and hope that they all differ :) )

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                          Chris KawaC 1 Reply Last reply
                          5
                          • Christian EhrlicherC Christian Ehrlicher

                            @Chris-Kawa Before creating the hash I would compare the filesize (and hope that they all differ :) )

                            Chris KawaC Online
                            Chris KawaC Online
                            Chris Kawa
                            Lifetime Qt Champion
                            wrote on last edited by
                            #14

                            @Christian-Ehrlicher Good idea. You could use the size as initial hash value and only do a "full" hash for hash conflict resolution (caching the result of course).

                            1 Reply Last reply
                            3
                            • A Offline
                              A Offline
                              Ayush Gupta
                              wrote on last edited by
                              #15

                              @Chris-Kawa Thanks

                              1 Reply Last reply
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