Number of elements in a list of list

[amleto]

vector<vector<int>> lotsOfInts;
// ...
size_t outerVectorSize = lotsOfInts.size();
size_t firstInnerVectorSize = lotsOfInts.begin()->size();

vector<vector<int>> lotsOfInts;
// ...
size_t outerVectorSize = lotsOfInts.size();
size_t firstInnerVectorSize = lotsOfInts.begin()->size();

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hope you can figure it out from that.

This is trivial c++ and definitely not Qt programming specific. Please consider better which forum you ask these questions in.