C++ Two Dimensional std::vector best practices

Question

I am building an app that needs to have support for two dimensional arrays to hold a grid of data. I have a class Map that contains a 2d grid of data. I want to use

Answer 1

Use a vector and translate the 2 dimensions to one dimension. E.g. if your matrix has a width of W and a height of H, then mapping x,y to the index in the vector is simply x*W+y.

If your matrix is sparse you may want to use an std::map where the key is a pair (x and y).