Hangs the application when you press the button, can not understand why

I'm new to c++ and qt, but I want to learn. The essence of the problem: the application hangs when you click on the button, although before some edits worked adequately (rolling back edits did not help). As far as I understand it is because of the while loop, but nowhere can I find an answer on how to fix it.

The program itself, what I need to implement, is to write the interaction of predators and herbivores, for a start on a primitive level.

So, please help me with the problem of hanging the application.

Creating classes

class Grass
{...};
class Predator
{...};
class Herbivorous
{...};

Button click processing

void MainWindow::on_pushButton_clicked()
{
    int kol_grass = ui->lineEdit_11->text().toInt(), kol_weeks = 0, t, t_x, t_y, kol_H = ui->lineEdit->text().toInt(), kol_P = ui->lineEdit_2->text().toInt(), k = 0, kk = 0;
    list<Herbivorous> lst_H;
    list<Predator> lst_P;
    list<Grass> lst_G;

    int kol_die_P_hungry = 0, kol_die_H_hungry = 0, kol_die_P_age = 0, kol_die_H_age = 0, eaten = 0;
    int years = 0;

    qsrand(QDateTime::currentMSecsSinceEpoch());

    //resize dynamic lists
    lst_H.resize(kol_H);
    lst_P.resize(kol_P);
    lst_G.resize(kol_grass);

    //creating list iterators
    list<Herbivorous>::iterator i = lst_H.begin();
    list<Herbivorous>::iterator j = lst_H.begin();
    list<Predator>::iterator ii = lst_P.begin();
    list<Predator>::iterator jj = lst_P.begin();
    list<Grass>::iterator grass_it = lst_G.begin();

    //creating grass objects
    for (; grass_it != lst_G.end(); grass_it++)
    {
        ...
    }

    grass_it = lst_G.begin();

    //creating herbivore objects
    for (; i != lst_H.end(); i++)
    {
        ...
    }

    //creating predator objects
    for (; ii != lst_P.end(); ii++)
    {
        ...
    }

    i = lst_H.begin();
    ii = lst_P.begin();

Then the same cycle

Apparently because of it hangs tightly application when you click on the button. What am I doing wrong?

    //as long as both animal species are alive, simulate life
    while (lst_H.size() > 0 && lst_P.size() > 0)
    {
        //grass rendering
        for (; grass_it != lst_G.end(); grass_it++)
        {
            if (grass_it->GetValue() != .0)
            {
                QTableWidgetItem * grass = new QTableWidgetItem();
                grass->setBackground(Qt::green);
                ui->tableWidget->setItem(grass_it->GetY(), grass_it->GetX(), grass);
            }
        }

        grass_it = lst_G.begin();

        //once a month grass replenishment
        if (kol_weeks % 4 == 0)
        {
            grass_it = lst_G.begin();

            for(; grass_it != lst_G.end(); grass_it++)
            {
                grass_it->Recovery();
            }

            grass_it = lst_G.begin();
        }

        //once a month check for starvation
        if (kol_weeks % 4 == 0)
        {
            i = lst_H.begin();

            for (; i != lst_H.end(); i++)
            {
                if (i->GetHungry() <= 0)
                {
                    i->SetInLife(false);//смерть от голода

                    kol_die_H_hungry++;
                }
                else
                {
                    i->SetAge(i->GetAge() + 1);//+1 год
                }
            }

            i = lst_H.begin();

            ii = lst_P.begin();

            for (; ii != lst_P.end(); ii++)
            {
                if (ii->GetHungry() <= 0)
                {
                    ii->SetInLife(false);//смерть от голода

                    kol_die_P_hungry++;
                }
                else
                {
                    ii->SetAge(ii->GetAge() + 1);//+1 год
                }
            }

            ii = lst_P.begin();
        }

        //once a year old age check
        if (kol_weeks == 48)
        {
            i = lst_H.begin();
            kol_weeks = 0;
            years++;

            for (; i != lst_H.end(); i++)
            {
                if (i->GetAge() >= ui->lineEdit_3->text().toInt())
                {
                    i->SetInLife(false);//смерть от старости

                    kol_die_H_age++;
                }
                else
                {
                    i->SetAge(i->GetAge() + 1);//+1 год
                }
            }

            i = lst_H.begin();

            ii = lst_P.begin();

            for (; ii != lst_P.end(); ii++)
            {
                if ((ii->GetAge() >= ui->lineEdit_10->text().toInt()) || (ii->GetHungry() <= 0))
                {
                    ii->SetInLife(false);//смерть от старости или от голода

                    kol_die_P_age++;
                }
                else
                {
                    ii->SetAge(ii->GetAge() + 1);//+1 год
                }
            }

            ii = lst_P.begin();
        }

        //movement of herbivores
        for (; i != lst_H.end(); i++)
        {
            QTableWidgetItem * noherbivorous = new QTableWidgetItem();
            noherbivorous->setBackground(Qt::black);
            ui->tableWidget->setItem(i->GetY(), i->GetX(), noherbivorous);

            if (i->GetInLife() == true)
            {
                i->Direction();
                i->Hungry();

                QTableWidgetItem * herbivorous = new QTableWidgetItem();
                herbivorous->setBackground(Qt::white);
                ui->tableWidget->setItem(i->GetY(), i->GetX(), herbivorous);
            }
        }

        //moving predators
        for (; ii != lst_P.end(); ii++)
        {
            QTableWidgetItem * nopredator = new QTableWidgetItem();
            nopredator->setBackground(Qt::black);
            ui->tableWidget->setItem(ii->GetY(), ii->GetX(), nopredator);

            if (ii->GetInLife() == true)
            {
                ii->Direction();
                ii->Hungry();

                QTableWidgetItem * predator = new QTableWidgetItem();
                predator->setBackground(Qt::red);
                ui->tableWidget->setItem(ii->GetY(), ii->GetX(), predator);
            }
        }

        lst_H.remove_if([] (Herbivorous a) {return (a.GetInLife() == false);});//the removal of dead
        lst_P.remove_if([] (Predator a) {return (a.GetInLife() == false);});//the removal of dead

        i = lst_H.begin();
        j = lst_H.begin();

        //death of parents and birth of children (herbivores)
        for (; i != lst_H.end(); i++)
        {
            for (; j != lst_H.end(); j++)
            {
                if ((i->GetNumber() != j->GetNumber()) && (i->GetInLife() == true) && (j->GetInLife() == true) && (i->GetAge() >= i->GetMin_Rep()) && (i->GetAge() <= i->GetMax_Rep()) && (j->GetAge() >= j->GetMin_Rep()) && (j->GetAge() <= j->GetMax_Rep()))
                {
                    t_x = i->GetX() - j->GetX();
                    t_y = i->GetY() - j->GetY();

                    if (((t_x == 1) || (t_x == -1) || (t_x == 0)) && ((t_y == 1) || (t_y == -1) || (t_y == 0)))
                    {
                        i->SetInLife(false);
                        j->SetInLife(false);

                        //creating children
                        t = qrand() % (4 + 1);//от 0 до 4 детей

                        for (int u = 0; u < t; u++)
                        {
                            Herbivorous child;

                            child.SetInLife(true);
                            child.SetX(qrand() % (234 + 1));//рандом
                            child.SetY(qrand() % (144 + 1));//рандом
                            child.SetAge(1);
                            child.SetFood(ui->lineEdit_6->text().toDouble());
                            child.SetNumber(kk);
                            child.SetMax_Rep(ui->lineEdit_4->text().toInt());
                            child.SetMin_Rep(ui->lineEdit_5->text().toInt());

                            k++;

                            lst_H.push_back(child);
                        }
                    }
                }
            }

            j = lst_H.begin();
        }

        ii = lst_P.begin();
        jj = lst_P.begin();

        //death of parents and birth of children (predators)
        for (; ii != lst_P.end(); ii++)
        {
            for (; jj != lst_P.end(); jj++)
            {
                if ((ii->GetNumber() != jj->GetNumber()) && (ii->GetInLife() == true) && (jj->GetInLife() == true) && (ii->GetAge() >= ii->GetMin_Rep()) && (ii->GetAge() <= ii->GetMax_Rep()) && (jj->GetAge() >= jj->GetMin_Rep()) && (jj->GetAge() <= jj->GetMax_Rep()))
                {
                    t_x = ii->GetX() - jj->GetX();
                    t_y = ii->GetY() - jj->GetY();

                    if (((t_x == 1) || (t_x == -1) || (t_x == 0)) && ((t_y == 1) || (t_y == -1) || (t_y == 0)))
                    {
                        ii->SetInLife(false);
                        jj->SetInLife(false);

                        //creating children
                        t = qrand() % (4 + 1);//от 0 до 4 детей

                        for (int u = 0; u < t; u++)
                        {
                            Predator child;

                            child.SetInLife(true);
                            child.SetX(qrand() % (234 + 1));//рандом
                            child.SetY(qrand() % (144 + 1));//рандом
                            child.SetAge(1);
                            child.SetFood(ui->lineEdit_8->text().toDouble());
                            child.SetNumber(k);
                            child.SetMax_Rep(ui->lineEdit_9->text().toInt());
                            child.SetMin_Rep(ui->lineEdit_7->text().toInt());

                            kk++;

                            lst_P.push_back(child);
                        }
                    }
                }
            }

            jj = lst_P.begin();
        }

        ii = lst_P.begin();
        j = lst_H.begin();

        //hunting of predators on herbivores
        for (; ii != lst_P.end(); ii++)
        {
            if (ii->GetHungry() < 1)
            {
                for (; j != lst_H.end(); j++)
                {
                    if ((ii->GetInLife() == true) && (j->GetInLife() == true))
                    {
                        t_x = ii->GetX() - j->GetX();
                        t_y = ii->GetY() - j->GetY();

                        if (((t_x == 1) || (t_x == -1) || (t_x == 0)) && ((t_y == 1) || (t_y == -1) || (t_y == 0)))
                        {
                            j->SetInLife(false);
                            ii->SetHungry(ii->GetHungry() + 1);
                            eaten++;
                        }
                    }
                }
            }

            j = lst_H.begin();
        }

        grass_it = lst_G.begin();

        //hunting herbivores on the grass
        for (; j != lst_H.end(); j++)
        {
            if (j->GetHungry() < 1)
            {
                for (; grass_it != lst_G.end(); grass_it++)
                {
                    if ((grass_it->GetValue() > 0) && (j->GetInLife() == true) && (j->GetX() == grass_it->GetX()) && (j->GetY() == grass_it->GetY()))
                    {
                        if (grass_it->GetValue() > 0.5)
                        {
                            j->SetHungry(j->GetHungry() + 0.5);
                            grass_it->SetValue(grass_it->GetValue() - 0.5);
                        }
                        else
                        {
                            j->SetHungry(j->GetHungry() + grass_it->GetValue());
                            grass_it->SetValue(0);
                        }
                    }
                }
            }

            j = lst_H.begin();
        }

        i = lst_H.begin();
        ii = lst_P.begin();
        grass_it = lst_G.begin();

        //summary of interim results
        ui->label_11->setText("The number of herbivores: " + QString::number(lst_H.size()));
        ...

        QEventLoop loop;
        QTimer::singleShot(100, &loop, SLOT(quit()));
        loop.exec();

        kol_weeks++;
    }
}```