QT generate random numbers (random strings) within the specified range

1. Purpose

   Writing QT Project time , Generating random numbers and random strings is a very common requirement , Use qrand Function can realize , But if you don't use seeds , The resulting random number is not a real random number , It's a fixed number . Usually , We will use the current time as the seed of random numbers , To produce real random numbers

2. Generate a random number in a specified range

Qt The code for generating random numbers is as follows ：

int getRandom(int min,int max)
{
    
    qsrand(QTime(0, 0, 0).secsTo(QTime::currentTime()));

    int num = qrand()%(max-min);
    qDebug()<<num+min;
}

3. Generate a random array that does not repeat

Store the generated random number in the array , Every time a new random number is generated , Check whether the number is included in the random number sequence table
If included, regenerate , Until a new random number is generated .

int getRandom(int min,int max)
{
    
    QList<int> list;
    int i,j;
    bool res = true;
    qsrand(QTime(0, 0, 0).secsTo(QTime::currentTime()));

    for (int i=0; i<10; i++) {
    
        int num = qrand()%(max-min)+min;
        list.append(num);

        while(res)
        {
    
            for(j=0;j<i;j++)
            {
    
                if(list[i]==list[j])
                    break;
            }

            if(j<i)
            {
    
                list[i] = qrand()%(max-min)+min;
            }
            if(j==i)
                res=!res;
        }
    }

}

4. Generate random strings

The random string generation code is as follows ：

QString getRandomString(int length)
{
    
    qsrand(QDateTime::currentMSecsSinceEpoch());

    const char ch[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int size = sizeof(ch);

    char* str = new char[length + 1];

    int num = 0;
    for (int i = 0; i < length; ++i)
    {
    
        num = rand() % (size - 1);
        str[i] = ch[num];
    }

    QString res(str);
    return res;
}