Ways to initialise a 2D vector

• vector<vector >vec(row,vector(col,’#’));

  Here row and col are the sizes of the 2D vector along its two axes

• The second way: set the size with resize, then assign values in a loop

  vector<vector<char> >vec1;
  vec1.resize(row);
  for(int i=0;i<vec1.size();i++)
    vec1[i].resize(col);
  for(int i=0;i<row;i++)
    for(int j=0;j<col;j++)  vec1[i][j]='#';