In C++17, the new map::extract
function lets you change the key.
Example:
std::map<int, std::string> m{ {10, "potato"}, {1, "banana"} };
auto nodeHandler = m.extract(10);
nodeHandler.key() = 2;
m.insert(std::move(nodeHandler)); // { { 1, "banana" }, { 2, "potato" } }