QStringList multiple entries and comparison - qt5

Question

I am using QInputDialog::getText to allow the user to input a string. The user should enter an arbitrary number of comma separated integers.
Then I would like to check if there is a duplicate.
In order to convert the input to integers, I have tried the following:
Split the input into a list using the QString::split with comma as an argument
Iterate over the elements of the QStringList
for (int i = 1; i <= list.count(); i++)
{
list.at(i).toInt();
}
The loop leads to a crash.
How to fix this?

Answer 1

Cause
Because the element index in the list is zero-based, i.e. starts from 0 and runs up to count - 1, your loop tries to access a non-existing element with index count and your program crashes.
Solution
Either change
for (int i = 1; i <= list.count(); i++)
to
for (int i = 0; i < list.count(); i++)
or even better, use a ranged for
for (const QString &substr : list)
Then use QList::takeFirst() and QList::contains in a while loop to check for duplicates.
Example
Here is an example I have prepared for you:
#include <QApplication>
#include <QInputDialog>
#include <QMessageBox>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
const QString &str(QInputDialog::getText(nullptr, "Input integers",
"Enter comma separated integers."
" Do not use spaces."));
QList<int> numbers;
bool hasDuplicate = false;
for (const QString &substr : str.split(','))
numbers.append(substr.toInt());
while (numbers.count() && !hasDuplicate)
hasDuplicate = numbers.contains(numbers.takeFirst);
QMessageBox::information(nullptr, "Result",
hasDuplicate ? "There is at least one duplicate"
: "All numbers are unique");
return 0;
}
Result
For the example input of
11,22,33
this message is shown
For the example input of
11,22,33,22
this message is shown