c++ - What does this vector push_back statement mean? -

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waht following mean?

vector<vector<pair<int, int>>> graph; graph.push_back(vector<pair<int, int>>()); // statement mean?

i wondering because statement didn't have values. can see rest of code browsing initialized locations being referenced later in code. that's pretty thought, not sure. sorry if newbie question, i'm new vectors. replies.

it "adds" newly initialized vector<pair<int,int>> "back" of vector name graph (i.e. after last entry, if any).


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