C++ value as map: Value is not updating in second map

I've C++ STL map with value as another map. I want to updated the value of inner map.

When inner map values is update and print immediately, it show updated value. But after that when a display function is called, it doesn't show the updated value. Not sure what I'm missing.

   #include <iostream>
   #include <map>
 
   typedef  std::map <std::string, std::string> poolNameApnNameT ;
  
   class A
   {
     public:
       struct S
      {
        std::map <std::string, poolNameApnNameT>apnPoolValidationDb;
      }s;
      void PrintfMe();
  };
 
  void A::PrintfMe()
  {
    for(auto x: s.apnPoolValidationDb)
    {
      std::cout <<"main: "<<x.first << std::endl;
      for(auto y: x.second)
      {
        std::cout <<"Inner: " <<y.first.c_str() <<" "<<y.second.c_str() << std::endl;
      }
 
    }
  }
 
  int main()
  {
    A a;
 
    a.s.apnPoolValidationDb.emplace(
        std::make_pair((char*)"pool1",
          poolNameApnNameT({ std::make_pair((char*)"pool2","xx")})
          ));
 
    a.s.apnPoolValidationDb.emplace(
        std::make_pair((char*)"pool2",
          poolNameApnNameT({ std::make_pair((char*)"pool1","zz")})
          ));
 
   
    a.PrintfMe();
   
 
   /* search key and updated value's value(inner map).*/
    for(auto search: a.s.apnPoolValidationDb)
    {
      auto search2 = search.second.find("pool2");
      if(search2 != search.second.end())
      {
        std::cout<<"found: " <<search2->first<<std::endl;
        std::cout<<"Updating: " <<search2->second<<std::endl;
        search2->second.assign((char*)"yy"); // Update using assign()
        std::cout<<"After Update " <<search2->second.c_str()<<std::endl;
 
        search.second[search2->first] = "OO"; // Update using []
        std::cout<<"After Update " <<search2->second.c_str()<<std::endl;
    }
    }
 
    std::cout<<std::endl;
 
    a.PrintfMe();
 
      return 0;
  }

Output: main: pool1
Inner: pool2 xx main: pool2 Inner: pool1 zz

found: pool2 Updating: xx After Update yy After Update OO

main: pool1 Inner: pool2 xx main: pool2 Inner: pool1 zz <<< should be OO instead of zz