how to insert elements in a 2d vector?

[tinie]

I encounter problems in inserting elements in a 2d vector. For example I want to insert 99 in v[2][5], how would I do it? What I have is this code:

 
  #include <iostream>
#include <iomanip>
#include <vector>
 
int main()
{
  std::vector< std::vector<int> > v;
 
  for ( int i = 0; i < 10; i++ ) {
    v.push_back ( std::vector<int>() );
 
    for ( int j = 0; j < 10; j++ )
      v[i].push_back ( i + j );
  }
 
  std::vector< std::vector<int> >::iterator row_it = v.begin();
  std::vector< std::vector<int> >::iterator row_end = v.end();
 
  for ( ; row_it != row_end; ++row_it ) {
    std::vector<int>::iterator col_it = row_it->begin();
    std::vector<int>::iterator col_end = row_it->end();
 
    for ( ; col_it != col_end; ++col_it )
      std::cout<< std::setw ( 3 ) << *col_it;
    std::cout<<'\n';
  }
 
//line 27
 
}
 
 
 

I tried inserting the line v.at(2).insert( col_it-5, 99); at line 27, but what I get is a segmentation fault message (I'm doing this in Linux). I also tried v[2].insert(col_it-5, 99) and the same thing happened. What I need is to insert not to overwrite the contents of v[2][5].
Can somebody tell me what I'm doing wrong. Any other suggestions on inserting elements on a 2d vector will be greatly appreciated.

[Ganon11]

Are you sure you should be writing col_it - 5? Also, where in the program are you trying to insert this? You may be attempting to do this at a point when col_it is not pointing to an element in the 3rd row (index 2) of the vector.