Find mapped value of map

Question

Is there a way in C++ to search for the mapped value (instead of the key) of a map, and then return the key? Usually, I do someMap.find(someKey)->second to get the value, but here I want to do the opposite and obtain the key (the values and keys are all unique).

Answer 1

Because of how a map is designed, you'll need to do the equivalent of a search on unordered data.

for (auto it = someMap.begin(); it != someMap.end(); ++it)
    if (it->second == someValue)
        return it->first;

Or with structured bindings (available since C++17) (suggested in lubgr's answer):

for (const auto& [key, value] : someMap)
    if (value == someValue)
        return key;