How to initialize a vector of vectors in a structure?

Question

If I have an NxN matrix

vector< vector<int> > A; 

How to initialize it?

I tried without success:

  A = new vector(dimension); 

neither:

  A = new vector(dimension,vector<int>(dimension)); 

Answer 1

You use new for dynamic allocation. It returns a pointer pointing to a dynamically allocated object.

You have no reason to use new , since A is an automatic variable. You can simply initialize A using your constructor:

 vector<vector<int> > A(dimension, vector<int>(dimension)); 

Answer 2

Like this:

 #include <vector> // ... std::vector<std::vector<int>> A(dimension, std::vector<int>(dimension)); 

(Pre-C ++ 11, you need to leave a space between the angle brackets.)