For a quick solution involving no external libraries, you can use hash<std::string> to hash strings. It’s defined by including the header files hash_map or unordered_map (or some others too).
#include <string>
#include <unordered_map>
hash<string> hasher;
string s = "heyho";
size_t hash = hasher(s);
If you decide you want the added security of SHA, you don’t have to download the large Crypto++ library if you don’t need all its other features; there are plenty of standalone implementations on the internet, just search for “sha implementation c++”.