Searching STL Map Inside STL Map Object :: C++

Hi.

How do you know if find() returns a valid element in a map that is inside a map? For example:

Code:

typedef std::map<int, int> mapIntInt;
typedef std::map<double, mapIntInt> mapDM;

mapIntInt mapOne;
mapOne.insert(std::pair<int, int>(0, 1));

mapDM mapTwo;
mapTwo.insert(std::pair<double, mapIntInt>(8.9, mapOne));

// Now I want to search mapOne, but first I need to search mapTwo for mapOne.

if (twoIterator != mapTwo.end())
{
   oneIterator = twoIterator->second.find(8.9);

   // How do you check if oneIterator points to a valid element?  
}

Given the example above, how do you know what if the search in the second map container (map inside of map) points to a valid element?

Thanks,
Kuphryn

I have not tested this code for any errors, but this is basically how it could be performed:

Code:

typedef std::map<int, int> mapIntInt;
typedef std::map<double, mapIntInt> mapDM;

mapIntInt mapOne;
mapOne.insert(std:pair<int, int>(0, 1));

mapDM mapTwo;
mapTwo.insert(std:pair<double, mapIntInt>(8.9, mapOne));

// loop through the main map from beginning to end
for (mapDM::const_iterator map2_iter = mapTwo.begin();
     map2_iter != mapTwo.end();
     ++map2_iter)
{
    // create an instance of the sub map for each loop through the main map
    const mapIntInt &map_one(*map2_iter).second);

    // assign an iterator to the value looked for
    const mapIntInt::const_iterator map1_iter = map_one.find(8.9);

    // if the iterator is not pointing at the end of the map, you found it
    if (map1_iter != map_one.end())
    {
        // found it!
    }
}

Hope that helps.

David

Okay. Thanks.

Your solution works!

// map1_iter != map_one.end()

Kuphryn