Let’s say in the map container one key stored. What will happen if we add another key with the same name as in the first key? Will an exception?

Answer 1, Authority 100%

Give advice – try to write a short test: you will find out, and you yourself attract a little:

# include & lt; iostream & gt;
#Include & lt; Map & GT;
TEMPLATE & LT; TYPENAME T1, TYPENAME T2 & GT;
Void Printmap (Const Std :: Map & LT; T1, T2 & GT; & amp; Container)
{
  STD :: COUT & LT; & LT; "CONTAINER SIZE =" & LT; & LT; container.size () & lt; & lt; STD :: ENDL;
  For (TypeName Std :: Map & LT; T1, T2 & GT; :: Value_Type Item: Container) {
    STD :: COUT & LT; & LT; "Key =" & lt; & lt; Item.First & LT; & LT; "Val =" & lt; & lt; item.second & lt; & lt; "";
  }
  STD :: COUT & LT; & LT; STD :: ENDL;
}
INT MAIN () {
  STD :: MAP & LT; STD :: STRING, INT & GT; MyMap;
  mymap.insert (std :: make_pair ("key1", 50));
  Printmap (MYMAP);
  MyMap.insert (Std :: Make_Pair ("Key1", 100));
  Printmap (MYMAP);
  MyMap ["Key1"] = 300;
  Printmap (MYMAP);
}

Result:

container size = 1
Key = Key1 Val = 50
CONTAINER SIZE = 1
Key = Key1 Val = 50
CONTAINER SIZE = 1
Key = Key1 Val = 300

It can be seen that Map :: Insert () will not change the value according to the existing key, Map :: Operator [] will restart