map of maps ??

in case of single map, to see whether a key exists or not mapname.count(keytofind) is used

Code:

map<int,bool>rb;
map<int,bool>::iterator rb_it;

rb.insert(make_pair(5,true));
rb.insert(make_pair(7,false));
rb.insert(make_pair(3,true));

int numtofind=7;
if(rb.count(numtofind))
{
          rb_it=rb.find(numtofind);
          cout<<"\n First= "<<(*rb_it).first<< "  Second=  "<<  (*rb_it).second ;
}
else
{
           cout<<"\n The key " << numtofind <<" does not exist in map" ;
}

but in case of map of maps, how a key has to be find ??

Code:

map<int,map<int,map<int, bool> > >r;
 r[3][4][3]=true;    
 r[3][2][3]=true;
 r[3][3][3]=true;

how to see whether a particular key exists or not??

how to see whether a particular key exists or not??

You call find() for each nested map:

Code:

// find r[3][2][3]
if (r.find(3) != r.end()) {
  if (r[3].find(2) != r[3].end()) {
    if (r[3][2].find(3) != r[3][2].end())
      cout << "Found!\n";
  }
}

You might want to wrap that in a function.