检查以下代码:stringtoLowerCase(conststring&str){stringres(str);inti;for(i=0;ileagues;set::iteratoriter;leagues.insert("BLeague");leagues.insert("aLeague");//leagues={"aLeague","BLeague"}leagues.insert("ALeague");for(iter=leagues.begin();iter!=leagues.end();iter++)cout输出是:aLeagueBLeague这让我很震惊。我认为(并期待)输