Traversing directories and their sub-directories - c++

Question

I traverse directories and their sub-directories using this piece of code. I do it in order to get path of only one random file from each end-sub-directories and pass to next end-sub-directory. But, in my implementation, it traverses all the files in end-sub-directories.
For example, from /cars/bmw/model1/ directory , it is enough to get just /cars/bmw/model1/f.png path.
QDirIterator it(selectedReferenceFullDirectory, QDir::Files, QDirIterator::Subdirectories);
while(it.hasNext())
{
...
}
My sub-directories are like:
/cars/bmw/model1/h.png
/cars/bmw/model1/f.png
/cars/bmw/model2/q.png
/cars/bmw/model1/hb/a.png
/cars/bmw/model1/sed/y.png
/cars/audi/model2/sed/y.png
...
So, there is no certain number of sub-diretory. Since there are tons of photos inside the directories, while loop takes long time. Do you have any idea to have better performance? Thank in advance

Answer 1

I propose to iterate not over all files, but over sub directories only. For each directory just take a single file (randomly). Here is how I would do it (simplest solution):
QStringList randomFiles(const QString &path)
{
QDirIterator it(path, QDir::AllDirs | QDir::NoDotAndDotDot,
QDirIterator::Subdirectories);
QStringList filePaths;
while (it.hasNext())
{
it.next();
QDir dir(it.filePath());
auto files = dir.entryInfoList(QDir::Files);
if (files.size() > 0)
{
// Take the first file from each directory.
// This might be a random file too, though.
filePaths.append(files.at(0).absoluteFilePath());
}
}
return filePaths;
}