operator <overload for std :: map的int类型比较？ （我希望它按降序排序..）

Question

I have encountered a problem that I want to define a map, that is sorted internally by the first's descending order. if the first is not a primary type, like if it's a class, I can just overload the "<" within that class, but I don't know how to deal with the int type. Any suggestion?

Thanks a lot!!

Answer 1

Add a comparator:

#include <functional>
map<int, value_type, greater<int>> m;

The default is less<int> .

Answer 2

You can specify a comparator when you create the map (it's an optional constructor argument).

eg:

bool my_compare(int x, int y) { return y < x; }

std::map<int,T,bool(*)(int,int)> my_map(my_compare);

Notice that I've needed to explicitly specify a 3rd template parameter as well.

[ Note: I would strongly advise that you don't overload the < operator to perform > ... ]

Answer 3

查看std :: less实现： http ： //www.cplusplus.com/reference/std/functional/less/您可以编写自己的比较器并将其与map一起使用。