c++ - Search for value in multi map -

suppose have following:

class foo { public:     foo(int x) {         _x = x;     }     int _x;     }  int main() {     multimap<string, foo> mm;     foo first_foo(5);     foo second_foo(10);      mm.insert(pair<string, foo>("a", first_foo));     mm.insert(pair<string, foo>("a", second_foo));      foo third_foo(10);  } 

what's nice way of checking if third_foo key "a" in multimap?

use multimap::equal_range fetch range of iterators entries have key "a". use any_of check if of values compare equal foo want.

auto const& r = mm.equal_range("a"); bool found = std::any_of(r.first, r.second,                          [&third_foo](decltype(mm)::value_type const& p) {                              return p.second._x == third_foo._x;                          });