C++:Load two demensional array from file?

$ cat bar.txt
3 2
1 2
3 4
5 6
$ cat bar.cpp
#include <iostream> 
#include <fstream>
#include <vector>
using namespace std; 

int main(void) 
{
  vector<vector<int> > mat;
  ifstream fin("bar.txt");
  int rows, cols;
  if ( fin >> rows >> cols ) {
    for ( int r = 0 ; fin && r < rows ; r++ ) {
      vector<int> row;
      for ( int c = 0 ; fin && c < cols ; c++ ) {
        int temp;
        if ( fin >> temp ) {
          row.push_back(temp);
        }
      }
      mat.push_back(row);
    }
  }
  cout << "Number of Rows = " << mat.size() << endl;
  cout << "Number of Cols = " << mat[0].size() << endl;
  return 0;     
}
$ ./a.out 
Number of Rows = 3
Number of Cols = 2