How to initialize all elements of a two-dimensional array to a particular value?

You can use std::fill:

for(auto &arr : two_dim)
    std::fill(std::begin(arr), std::end(arr), value);

This will work for many arrays and containers, like std::vector, std::array, and C arrays.

Also note that you can use memset to initialize all elements of an array to values other than -1 and 0. It's just that all the bytes in each element will have the same value, like 0x12121212.