CODEWITHSUNDEEP
c++vector
Andrew Lalis
Andrew Lalis

Reputation: 974

Appending a New Vector to a Vector

I'm creating a vector that itself will contain a vector, using this code:

vector<vector<short>> pixelData;

However, I start with an empty vector, and I would like to append a new vector as the first element, but I don't know how to construct a vector without assigning it to a variable. Right now, I'm doing:

pixelData.push_back(vector<short> (x, y));

Where pixelData is my containing vector, and I'm constructing a new vector inside with two short values.

Upvotes: 1

Views: 98

Answers (2)

songyuanyao
songyuanyao

Reputation: 172884

If you want to append a new vector, which contains two elements with value x and y, you should use initialization list (since C++11),

pixelData.push_back(vector<short> {x, y});

or just

pixelData.push_back({x, y});

Check the constructors of std::vector here.

Upvotes: 3

Jack
Jack

Reputation: 133567

Actually you are not constructing a vector with 2 short values, you are invoking this constructor:

explicit vector::vector(size_type count, const T& value = T())

which initializes the vector with a capacity of count by coping value to each cell.

To create an empty vector just call the empty constructor, eg vector<short>(), but if you know the capacity just use it, eg vector<short>(size) to avoid internal reallocation.

Upvotes: 1

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