Iterating through a 2d Vector row

Question

I am working on a homework assignment for my C++ class.

I am trying to iterate through a 2d multidimensional vector. I have all the data in the 2d vector which is size 7x7 i.e. 0-6 by 0-6,.

Problem is I need to output the contents of the 2d vector in the order of alphaV[0][0], alphaV[1][0], alphaV[2][0], etc.

When I try to use a nested For loop to process this vector I run into problems whereby the rows of the vector will not iterate, that is to say they remain at index 0.

So it keeps repeating alphaV[0][0], alphaV[0][0], alphaV[0][0], etc.

How do I go about iterating the columns in that pattern [0][0], [1][0], [2][0] ...?

Solution

Iterate over the vectors, this is the standard way of traversing containers:

void printVector(const std::vector< std::vector<int> > & vec)
{ 
    std::vector< std::vector<int> >::const_iterator row; 
    std::vector<int>::const_iterator col; 
    for (row = vec.begin(); row != vec.end(); ++row)
    { 
         for (col = row->begin(); col != row->end(); ++col)
         { 
            std::cout << *col; 
         } 
    } 
} 

More information on iterators can be found here: http://www.cplusplus.com/reference/iterator/