Print size of a vector through an iterator - c++

Question

I'm trying to print the size of a vector. Sounds easy, but the vector is in a map.
Currently I have an iterator on a map looking like this:
map<string, vector<map<vector<string> , vector<string> > > >::iterator it;
I am trying to display the size like this:
EDIT:
The iterator is intialised like this: it = csvMap.find(commandList.at(lineCount));
cout<<"Size of vector in Map after modifying: " << it->second.size() <<"\n"<<endl;
It's not working, the program crashes.
I think a way would be to make a temp vector and fill it with the value it->second;
But just to get the size is kind of wasting space isn't it?
Is there a better way to do so?
Thanks in advance!
EDIT2: removed old code
EDIT 3: new code:
map<vector<string> , vector<string> > parameterMap;
parameterMap.insert(pair<vector<string> , vector<string> > (
part1_input, part2_output));
map<string, vector<map<vector<string> , vector<string> > > >::iterator it;
cout<<"\nSize of CSV Map before modifying: " << csvMap.size() <<endl;
//cout<<"Size of vector in CSV Map before modifying: " << it->second.size() <<"\n"<<endl;
if(csvMap.size() == 0)
{
/*
* csvMap is empty -> no need to search for something. Just insert the fist entries
*/
listedParameterMap.insert(listedParameterMap.end(), 1, parameterMap);
csvMap.insert(pair<string, vector<map<vector<string> ,
vector<string> > > > (commandList[lineCount],
listedParameterMap));
cout<<"CSV Map size: " << csvMap.size() <<endl;
}
else
{
/*
* Search if the Command is already available, if not,
* add it to the map with its corresponding list of maps (in/output values)
* find returns map::end if key is not found
*/
cout<<"Checking if: " << commandList.at(lineCount) << " is already in the list \n" << endl;
it = csvMap.find(commandList.at(lineCount));
if (it == csvMap.end())
{
/*
* it = csvMap.end() is true
* The command isn't found
*/
cout<< commandList.at(lineCount) << " command not available. Inserting it! \n" << endl;
listedParameterMap.insert(listedParameterMap.end(), 1, parameterMap);
csvMap.insert(pair<string, vector<map<vector<string> ,
vector<string> > > > (commandList[lineCount],
listedParameterMap));
}
else
{
/*
* it != csvMap.end()
* The command is found. Append the parameterMap to the vector in the map
*/
cout<< commandList.at(lineCount) << " is already in the list! Appending parameters on pos: "<< it->second.size()-1<< "\n" << endl;
it->second.push_back(parameterMap);
}
}
cout<<"\nSize of CSV Map after modifying: " << csvMap.size() <<endl;
cout<<"Size of vector in CSV Map after modifying: " << it->second.size() <<"\n"<<endl;
I hope someone is still reading this...
I found now that it.second seems to be the problem on the first interation. But I don't get why.
Code snippet (also in the code above):
if(csvMap.size() == 0)
{
/*
* csvMap is empty -> no need to search for something. Just insert the fist entries
*/
listedParameterMap.insert(listedParameterMap.end(), 1, parameterMap);
csvMap.insert(pair<string, vector<map<vector<string> ,
vector<string> > > > (commandList[lineCount],
listedParameterMap));
cout<<"CSV Map size: " << csvMap.size() <<endl;
cout<<"listedParameterMap: " << listedParameterMap.size() <<endl;
cout<< commandList.at(lineCount) << " is already in the list! Appending parameters on pos: "<< it->second.size()<< "\n" << endl;
}
This seems not to work. Although its goning into it. Any idea why?
comanndList and listedParameterMap are as far as I see OK.

Answer 1

it = csvMap.find(commandList.at(lineCount));
if (it == csvMap.end()) {
cout << "not found\n";
}
else {
cout << "Size of vector in Map after modifying: " << it->second.size() << '\n';
}
Either when command isn't found or command is the last
No, the end iterator is not an item in the container.
string c = (*it).first;
Since this is after the iterator is the end iterator, you have undefined behavior when dereferencing it.

Answer 2

Your it is pointing to an invalid location. You need to initailize it with the map's iterator. Something like it = myMap.find("aaa"); //Replace it with actual key After doing the find you need to make sure you are having a valid iterator by checking it agains myMap.end().
EDIT
You are using uninitialized iterator here:
cout<<"Size of vector in CSV Map before modifying: " << it->second.size() <<"\n"<<endl;
Also, you can not dereference a iterator pointing csvMap.end(), it will result in crash again.
As per EDIT 3
You are still using the unitialized iterator / iterator pointing to end in if(csvMap.size() == 0) and if(it == csvMap.end()) case. You need to initialize the it with the return value of insert function like this:
it = csvMap.insert(....).first; in these cases.

Answer 3

Map iterators aren't invalidated unless you erased that specific element. That means that you did something else wrong.

Answer 4

Your collection is rather complex.
In order to check the size though you need to know there is an element there at all, i.e. find did not return "end" of your map. If it does, you cannot use the iterator returned.
Of course how you handle this is your own decision, eg return maybe -1 if the string was not found (with 0 indicating it was found but had no content).
Now you have edited your code I immediately spot a bug:
if (it == csvMap.end())
{
/*
* it = csvMap.end() > true
* Either when command isn't found or command is the last
*/
string c = (*it).first;
you cannot dereference end (which it is)