Read two parallel C++/STL: vectors/containers within a single (for) loop.

vector<string> vec1;
vector<string> vec2;

vec1.push_back("1");
vec1.push_back("2");
vec1.push_back("3");

vec2.push_back("one");
vec2.push_back("two");
vec2.push_back("three");

if (vec1.size()!=vec2.size()) { // are they parallel vectors;
    cerr << "Error size mismatch, vectors are not parallel!" << endl;
}
else {
  vector<string>::iterator vec1_iter=vec1.begin();
  for(vector<string>::iterator vec2_iter=vec2.begin();
      vec2_iter!=vec2.end();
      ++vec2_iter, ++vec1_iter) {
          cout << *vec1_iter << '\t' << *vec2_iter << endl;
  }
}

Program execution:

1       one
2       two
3       three