Creating a 2 dimensional Vector and accessing it

[forceface]

I've been trying to make a 2-d vector that would be a 10x10 and i could fill the vector(called nest) so that one of the indices could have more components than another other indices. But when i create the vector it makes every value in it zero. Here's my code

class Test {
  static int i;
  static int j;
 static vector<int> vec;
 static vector< vector<int> > nest;
  static int GetVec(int j) { return vec[j]; } 
 public:
  Test();
  ~Test(){};      
  static void PhillVec();
  static void TransferVec();  
};
#endif

void Test::PhillVec() {
 vec.resize(10);

    double random;
     for( int a=0; a<vec.size(); a++) { 
	  random = rand() % 10000;
	  double value = random/10000;  
	
    if( value < .5 ) vec[a]=1 ;
	else vec[a]=0;
   
	   }
   for (int j=0;j<vec.size();j++) {
   	   cout<< "vec " << j << "= " << vec[j] <<endl;  
    }
}

void Test::TransferVec () { ////here is the problem part of the code
 nest.resize(10);
 
 for(int l=0;l<10;l++)  {
        nest[l].resize(10); /////i think this makes my vectors full of zeros
        if(GetVec(l)==1){
        nest[l].push_back(1);
   cout<<"nest= "<<nest[l][i]<<endl;
    }
} 
    i++;
}

Test::Test(){
 for(int t=0;t<10;t++){
  PhillVec();
  TransferVec();    
}
}

int Test::j=0;
int Test::i=0;
vector<int> Test:: vec;
vector< vector<int> > Test:: nest;

int main() {
 srand( time(NULL) );
 Test();  
}

Any comments or suggestions would be great. Thank you.

[EricDu]

forceface wrote:

nest[l].resize(10); /////i think this makes my vectors full of zeros

Yes, you are right, vector<int>::resize() fills out each expanded element with value of int() which is 0. Nothing wrong here.

[forceface]

How do i then create a vector that is a 10x10 but that is completely empty?

[EricDu]

I understand that you want to create a 10x10 table, and each cell in the table is just a place holder, no any object is created at this moment. But it's impossible to directly use vector to do it. As long as you specify a size to a vector, then the vector creates objects right away, and each object is initialized with proper value. You need to define something like wrapper or referencer to approach your goal.

[forceface]

Could you possibly give me an example of what you were thinking?

[EricDu]

For example, if you define "vector<MyClass> aaa(2);", then aaa will contain 2 objects of MyClass, this means aaa is not empty because it has 2 objects already.

if you define "vector<MyClass*> bbb(2);", then bbb will contains 2 objects of "MyClass*", but not objects of MyClass, the default value for pointer here is NULL. Now bbb's size is 2, bbb is "a sort of empty" for object of MyClass. Here MyClass* is a referencer of MyClass.