converting list of strings representing numbers to set

user4592357

i have a list of numbers, i need to join the numbers into a string by _ character.
e.g.

QStringList lstStrings{"1", "2", "3"};
std::cout << QStringList(lstStrings.toSet().toList()).join('_').toStdString();

this prints 3_1_2. why does this happen?
i expect 1_2_3 to be printed.

Bonnie

Please take some time to read the documentation:

QSet is unordered, so an iterator's sequence cannot be assumed to be predictable. If ordering by key is required, use a QMap.

You can try

lstStrings.removeDuplicates();
lstStrings.sort();

But still, this sort will only sort them as strings, not numbers.

JonB

@user4592357 said in converting list of strings representing numbers to set:

this prints 3_1_2. why does this happen?

Because you went toSet().

i expect 1_2_3 to be printed.

All you needed for this is QStringList::join(). There is no sorting here.

std::cout << lstStrings.join("_");

user4592357

@JonB
the reason i used toSet() is that the items in my string list may be reordered, and i want to always get the same sequence from same items.
i guess not sorting is fine as long as i get the same result for same input.

SGaist

Hi,

You can use QCollator with the numerical mode activated for your numeric text sorting.