问题
I am looking for the highest key value (a defined by the comparison operator) of a std::map.
Is this guaranteed to be
map.rbegin()->first
?
(I am a bit shaky on reverse iterators, and how much freedom there is in the implementation of std::map)
If not, please advise. I cannot change the data structure.
回答1:
Yes. Map is a sorted container, the reverse iterator must return the elements in reverse (i.e. decreasing) order of their keys.
[Edit: as Charles Bailey points out in his answer, your code gives the greatest key if it exists - i.e. if the map is non-empty]
回答2:
Yes, but remember to check that map.rbegin() != map.rend().
回答3:
You can use following method :-
if(!map.empty())
(--map.end())->first;
来源：https://stackoverflow.com/questions/289715/last-key-in-a-stdmap