Does find() also return the last element of a map in C++?

问题

I'd like to use the find() method, to catch a particular element of my std::map()

Now the return value is either the element I was looking for, or it it points to the end of the map if the element hasn't been found (C.f.: http://www.cplusplus.com/reference/map/map/find/ ).

So I'm using these two information whether to decide if an element is in the map or not. But what happens if the element is already inside but at the very end ? My if-query would then decide that it's not existing and therefor my program will be made up.

Am I getting this routine right, and if, how to prevent it ?

Thanks for your support

回答1:

The last element in any container is not the same as the containers end iterator. The end iterator is actually one step beyond the last element in the container.

That means you can rest easily, and use find without worries. If the element you look for is the last element, you will get what you search for.

回答2:

You can actually use if(!map.count(elem)) to check whether elem is present in the map, count() returns 0 if elem is not present in the map while find() returns an iterator which has to been compared to the end iterator, i.e., if(map.find(elem) != map.end()).

来源：https://stackoverflow.com/questions/24823197/does-find-also-return-the-last-element-of-a-map-in-c