#include <map>
  multimap operator=(const multimap& c2);
  bool operator==(const multimap& c1, const multimap& c2);
  bool operator!=(const multimap& c1, const multimap& c2);
  bool operator<(const multimap& c1, const multimap& c2);
  bool operator>(const multimap& c1, const multimap& c2);
  bool operator<=(const multimap& c1, const multimap& c2);
  bool operator>=(const multimap& c1, const multimap& c2);

All of the C++ containers can be compared and assigned with the standard comparison operators: ==, !=, <=, >=, <, >, and =. Performing a comparison or assigning one multimap to another takes linear time.

Two multimaps are equal if:

1. Their size is the same, and
2. Each member in location i in one multimap is equal to the the member in location i in the other multimap.

Comparisons among multimaps are done lexicographically.