As the title says, i'm trying to randomly generate Sudoku (in this example 4x4) and i know how to do it, kinda, i believe it should work, but for some reason my program crashes when i run it ... Sometimes it works and when it does Sudoku is then spawned like this :

sudokuWorking.PNG
https://imgur.com/Ctf0046

But when it doesn't work, which is like 70% of the time, then it crashes and its like this :

sudokuCrash.jpg
https://imgur.com/2ksNiMQ

I put qDebug() in my while loop and i realized that my loop keeps repeating itself and idk why....
In Igrica.h file i defined stiriRandom as int table of [4][4]. When i press 4x4 button, size is set to 4.

Qt Code: 
  1. void Igrica::randomTabela(){
  2.  
  3.     int random_number;
  4.     qDebug() << "size" << size;
  5.     if(size == 4){
  6.         qDebug() << "hi";
  7.         for(int i=0;i<size;i++){
  8.             for(int k=0;k<size;k++){
  9.  
  10.                 bool help = false;
  11.                 while(help == false){
  12.                     qDebug() << "um stuck here";
  13.                     random_number = (rand()%4)+1;
  14.  
  15.                     // checking if there is the same number as random_number in a row
  16.                     for(int j=0;j<size;j++){
  17.                         if(stiriRandom[j][k] == random_number){
  18.                             help = false;
  19.                             break;
  20.                         }else{
  21.                             help = true;
  22.                         }
  23.                     }
  24.                     // checking is there is another random_number in collumn
  25.                     if(help == true){
  26.                         for(int j=0;j<size;j++){
  27.                             if(stiriRandom[i][j] == random_number){
  28.                                 help = false;
  29.                                 break;
  30.                             }else{
  31.                                 help = true;
  32.                             }
  33.                         }
  34.                     }
  35.  
  36.                     if(help == true)
  37.                         stiriRandom[i][k] = random_number;
  38.                 }
  39.             }
  40.         }
  41.     }else if(size == 9){
  42.         qDebug() << "hi";
  43.         for(int i=0;i<size;i++){
  44.             for(int k=0;k<size;k++){
  45.  
  46.                 bool help = false;
  47.                 while(help == false){
  48.  
  49.                     random_number = rand()%9+1;
  50.  
  51.                     for(int j=0;j<size;j++){
  52.                         if(devetRandom[j][k] == random_number){
  53.                             help = false;
  54.                             break;
  55.                         }else{
  56.                             help = true;
  57.                         }
  58.                     }
  59.  
  60.                     if(help == true){
  61.                         for(int j=0;j<size;j++){
  62.                             if(devetRandom[i][j] == random_number){
  63.                                 help = false;
  64.                                 break;
  65.                             }else{
  66.                                 help = true;
  67.                             }
  68.                         }
  69.                     }
  70.  
  71.                     if(help == true)
  72.                         devetRandom[i][k] = random_number;
  73.                 }
  74.             }
  75.         }
  76.     }else if(size == 12){
  77.         for(int i=0;i<size;i++){
  78.             for(int k=0;k<size;k++){
  79.  
  80.             }
  81.         }
  82.     }
  83. }
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Igrica header file

Qt Code: 
  1. #ifndef IGRICA_H
  2. #define IGRICA_H
  3.  
  4. #include <QGraphicsView>
  5. #include <QGraphicsScene>
  6. #include <QObject>
  7. #include <QMouseEvent>
  8. #include <QGraphicsSceneMouseEvent>
  9. #include <QGraphicsScene>
  10. #include <QWidget>
  11. #include <QKeyEvent>
  12.  
  13. #include "polje.h"
  14. #include "igralec.h"
  15.  
  16. class Igrica: public QGraphicsView{
  17.     Q_OBJECT
  18. public:
  19.     Igrica(QWidget *parent=NULL);
  21.     Igralec *igralec;
  22.     void meni();
  23.     void zapolniTabelo();
  24.     void izpisiTabelo();
  25.     void randomTabela();
  26.     void narisiOdebeljeneCrte();
  27.     void naredimoFinishButton();
  28.     Polje *stiri[4][4];
  29.     Polje *devet[9][9];
  30.     Polje *dvanajst[12][12];
  31.     int stiriRandom[4][4];
  32.     int devetRandom[9][9];
  33.     int dvanajstRandom[12][12];
  34. public slots:
  35.     void start();
  36.     void meniFour();
  37.     void meniNine();
  38.     void meniTwelve();
  39.     void preveriZmago();
  40.  
  41. private:
  42.     int size;
  43.     int level;
  44. };
  45.  
  46. #endif // IGRICA_H
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Any help is appreciated !!!!!!!!!!!!!!!!!!!!!!