Question

Is possible to put a vector in the array element a[0],a[1]… (different vector in each a[x])?
And if possible, how do I access one element of the vector in a given a[n]?

Answer 1

Some of the possibilities you have:

// Static array of vectors (not a good practice though) 
std::vector<int> vec_array1[size];

// Or dynamic array of vectors (still not very c++ish and error prone)
std::vector<int> *vec_array2;
vec_array = new std::vector<int>[size];

// Or vector of vectors
std::vector<std::vector<int> > vec_array3(size);

// Or std::array of vectors (in c++11)
std::array<std::vector<int>, size> *vec_array4;

In any case, you can access the vectors using [] operator:

vec_array[0].push_back(5);

And the elements using two [] operators like:

vec_array[0][2] = 4;