map of lists of vectors

[BigMoon]

Hi all
I would like to do a map of lists of vectors

I know how long the vectors will be but I don't know how many vectors it will be for each key. Later I would like to get all the vectors that is on a certain key.
How do I push a vector to the bottom of a list on a map. I thought I could write it like this.

tmpvector[0]=a;
tmpvector[1]=b;
tmpvector[2]=c;
tmpvector[3]=d;
tmpvector[4]=e;
maptable[key].push_back(tmpvector); //tmpvector is 5 long 

It doesn't give any error except when I try to reach them later in the code by:

for ( itmap=maptable.begin() ; itmap != maptable.end(); ++itmap ) {
   cout << "Key = " << (*itmap).first << endl;  //This works fine but under it I would like to get all the vectors
   for ( itlist=itmap->second.begin() ; itlist != itmap->second.end(); ++itlist) {
      cout << (*itlist)[0] << " " << (*itlist)[1] << " " << (*itlist)[2] << " " << (*itlist)[3] << " " << (*itlist)[4] << endl;
   }
   cout << endl;
}

The variables in use is defined like this

vector<int> tmpvector;
tmpvector.reserve(5);
map<int,list<vector<int> > > maptable;
map<int,list<vector<int> > >::iterator itmap;
list<vector<int> >::iterator itlist;

Can anyone see what's wrong or how to do this or does anyone know of annother way to accomplish what I want to do?

[jsmith]

Out of curiosity, of what benefit is making the value a list of vectors? Why not just a single vector? Or a deque? Why split it
into a list of vectors?

[BigMoon]

Thanks for the quick answer. But it didn't help me much.

Do you mean only a map of vectors? I need access to all vectors that give a certain key. I also need access to them many times. For each key I will have a few different vectors (don't know how many) so that's why I thought it might be best with a map of lists of vectors.

Any idea what I do wrong?

The error msg I recieve is EXC_BAD_ACCESS when I try to reach (*itlist)[0] but I think it's the maptable[key].push_back(tmpvector); that is wrong

[bigearsbilly]

a map of a list of vectors?
my spider sense is tingling.

maybe youshould tell us what you are trying to do
rather than how you want it done.

[BigMoon]

I want to match certain ints that produce a key together with other ints that produce the same key.
so I have a nested for loop

for (a=1;a<100;a++) {
 for (b=1;b<100;b++) {
  for (c=1;c<100;c++) {
   for (d=1;d<100;d++) {
    for (e=1;e<100;e++) {
     // and these a to e produce a key so I want to store them in a map so I
     // later can reach them quickly and all of the a to e that produce the same key
     // some a to e produce the same key
    }
   }
  }
 }
}

// Here I go into a similar for loop
for (f=1;f<100;f++) {
 for (g=1;g<100;g++) {
  for (h=1;h<100;h++) {
   for (i=1;i<100;i++) {
    for (j=1;j<100;j++) {
     // and these f to j produce a key and if that key exist in my map I would like to match them with all the a to e at that produce the same key
    // a1, b1, c1, d1, e1 with f, g, h, i, j
    // a2, b2, c2, d2, e2, with f, g, h, i, j
    // a3, b3, c3, d3, e3, with f, g, h, i, j
    // a1 to e1 produce the same key as a2 to e2 and so on
    // I don't know how many a to e will produce the same key
    }
   }
  }
 }
}

That's why I thought a map of lists of vectors might be good.

Any ideas???

[m4ster r0shi]

So, you want more than one values associated to a specific key... Why not use a multimap then? ^(*)

http://cplusplus.com/reference/stl/multimap/

EDIT: ^(*) That is, a multimap of vectors of ints

[BigMoon]

I just started looking at that.

How do I then insert a vector and later access all the vectors at a certain key?

The important part of the program is that the accessing of the vectors is as fast as possible (All the a to e at a certain key).

[Zhuge]

http://cplusplus.com/reference/stl/multimap/equal_range/
The equal_range() method seems like it will give you two iterators, between which all of the vectors of the given key reside.

[BigMoon]

Great! Thanks m4ster r0shi and Zhuge!

I'm looking into it now but it seems I still get the EXC_BAD_ACCESS when trying to access the ints in the vector.

I edited the example you sent so it is a multimap of vectors like this

multimap<char,vector<int> > mymm;
multimap<char,vector<int> >::iterator it;
pair<multimap<char,vector<int> >::iterator,multimap<char,vector<int> >::iterator> ret;
vector<int> v;

v.reserve(5);
v[0]=1;
v[1]=2;
v[2]=3;
v[3]=4;
v[4]=5;
mymm.insert(pair<char,vector<int> >('a',v));
v[0]=11;
v[1]=12;
v[2]=13;
v[3]=14;
v[4]=15;
mymm.insert(pair<char,vector<int> >('b',v));
v[0]=21;
v[1]=22;
v[2]=23;
v[3]=24;
v[4]=25;
mymm.insert(pair<char,vector<int> >('b',v));
	
cout << "mymm contains:\n";
for (char ch='a'; ch<='b'; ch++) {
	cout << ch << " =>" << endl;
	ret = mymm.equal_range(ch);
	for (it=ret.first; it!=ret.second; ++it)
		for (int i=0; i<5; i++) {
			cout << " " << (*it).second[i]; //It compiles ok but here I get the EXC_BAD_ACCESS error
		}
		cout << endl;
	}
}

so I guess this mymm.insert(pair<char,vector<int> >('a',v)); or this (*it).second[i] is wrong.

when I do this mymm.insert(pair<char,vector<int> >('a',v)); does then the whole vector come into the multimap?

[BigMoon]

I solved it!

I changed

vector<int> v;
v.reserve(5);

to this

vector<int> v (5,0);

Even the map of list of vectors work now. So it was nothing really wrong with it.

But one last question. What do you think is faster? A multimap of vectors or a map of lists of vectors?

[jsmith]

A multimap of vectors has one less level of indirection. But, perhaps more importantly,
a multimap of vectors is easier to comprehend than a map of lists of vectors, though I
still wonder why you couldn't just have a map of vectors, essentially combining the vectors
whose keys are equal into a single vector.

[bartoli]

I always use this chart (http://www.liamdevine.co.uk/code/containers.php ) when i have to chose a new container.
Choosing the appropriate container depending on how you need to store and access data can improve your code performance, and make it easier to program.