How to make a map sort by value C++

Question

I was trying to make a map sort by value using a custom comparator but I couldn\'t figure out why I kept getting the error of \"no matching call to compareByVal\"

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Answer 1

If you want to sort a std::map by its value, then you are using the wrong container. std::map is sorted by the keys by definition.

You can wrap key and value:

struct foo {
    int key;
    int value;
};

and then use a std::set that uses a comparator that only compares foo::value.