plus use constexpr to define the compile time constant

size_t should be use for container indexes and container related
distances

some casts have to be reinterpret_casts because of type incompatibility
between unsigned char * and char *

ints unnecessarily reduce range of values for indexes

remove not needed cast

Map keys are exactly corresponding to vector indexes in the algorithm.

getRank used to return a class that was supposed to be compatible with
unsigned (and size_t) however now it is unsigned by itself

the field has its default value specified, no need for the initializer

int to char is expected so cast; double to in was incorrect should
return double

The common abreviation for microseconds is us.