dynamic array of vectors

Hi,
I would like to create a dynamic array of vectors. This is my code so far:

Code:

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std::vector<int> vectorInput; /*A vector containing the input from the file*/
std::vector<int> *vectorArray; /*A dynamic array containg the vector for the different nodes*/

vectorArray = new std::vector<int>[numberOfNodes];

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I would then like to read a file and put the different lines in different vectors and store the pointer to the vectors in the array.

Since I do not know the number of lines beforehand, I was wondering how to dynamically create the vectors. Thanks
Amish

Why not go with a vector of vectors?

Code:

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std::vector<std::vector<int> > vectorArray;

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don't forget you will need to populate a vector<int> before you pushback into your vector of vectors:

Code:

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vector<vector<int> > 2D_vector;
vector<int> 1D_vector;

1D_vector.push_back(42);
1D_vector.push_back(98);
1D_vector.push_back(22);

2D_vector.push_back(1D_vector);

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I fill up the 1D vector the first time around with data from the first line of a file and push it onto the 2D vector but what happens when I read a second line and I want to push the data onto a new 1D vector and push that 1D vector onto the 2D vector. I cannot use the same 1D_vector object else the old data is going to be overwritten. Thanks
Amish

Quote:

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I cannot use the same 1D_vector object else the old data is going to be overwritten.

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Why do you care?

Quote:

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Originally Posted by axr0284

I fill up the 1D array the first time around with data from the first line of a file and push it onto the 2D array but what happens when I read a second line and I want to push the data onto a new 1D vector and push that 1D vector onto the 2D vector. I cannot use the same 1D_vector object else the old data is going to be overwritten.

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Clear the 1D vector (with an invalid identifier name mentioned by The Brain) after pushing it; each 1D vector is saved when you push it back.

Quote:

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Why do you care?

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Just to clarify that: vectors make copies of the data. When you push_back(theData), the Data is copied, and the copy is inserted into the back of the vector. So, when you push_back() the 1d vector into your 2d vector, the 1d vector is copied, and the copy is inserted into the 2d vector. Thereafter, anything you do to the 1d vector has no effect on what's in the 2d vector.

I started out with good intentions for this post, but...

Code:

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#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>
#include <iterator>
using namespace std;

int main()
{
  vector<vector<int> > my2Dvector;
  ifstream file("file.txt");
  string line;
  while ( getline(file, line) )
  {
      istringstream iss(line);
      int value;
      vector<int> my1Dvector;
      while ( iss >> value )
      {
        my1Dvector.push_back(value);
      }
      my2Dvector.push_back(my1Dvector);
  }
  // (horrible, but an example)
  for ( vector<vector<int> >::size_type i = 0; i < my2Dvector.size(); ++i )
  {
      for ( vector<int>::size_type j = 0; j < my2Dvector[i].size(); ++j )
      {
        cout << my2Dvector[i][j] << ' ';
      }
      cout << '\n';
  }
}

/* file.txt
1 2 3
4 5 6 7
8 9
*/

/* my output
1 2 3
4 5 6 7
8 9
*/

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...it ended up like this. :(

interesting. I did not know vectors made copy of the data. I thought they used pointers or something. Thanks for the help everybody,
Amish