Moving object to front of vector pair string c++ - c++

Question

I have a question about moving an Object to the front in a vector pair. I already read that one post but I didnt know how to use it with vector pairs or better said how to do it with strings. I dont know how to point with an iterator at the position I need because in my code I also need a count number to compare the two strings or how is it possible to compare something like if(it==ite){..} (i would need 2 loops for my examples so I would name the other one "ite" just as an example.
I have a vector<pair<string,string>> Dictionary and a vector string Text where I go through the dictionary and try to find the same word from the text in the dictionary. I already accomplished that but now I need to move the element that I found in the dictionary to the front and delete it from its old position.
I´m not sure how to do it with vector pairs.
Here´s my code to understand what I mean:
for(size_t i=0;i<Text.size();i++){
for(size_t j=0;j<Duden.size();j++){
if(Text[i]==Duden[j].first){
uebersetzung.push_back(Duden[j].first);
if(Duden[j].first.length()<4){
uebersetzung.push_back(" ");}
if(Duden[j].first.length()<8){
uebersetzung.push_back("\t");} // These are only so it looks cleaner at the end
uebersetzung.push_back("\t\t\t\t: ");
uebersetzung.push_back(Duden[j].second);
uebersetzung.push_back("\n");
// Now here should be the code to rotate the vector so the found element is now at the first position and not at the found position
break;
}
}
}
"Duden" here is dictionary if you´re wondering. I want to swap position of the elements from the dictionary so if the word occurs again in the text it doesnt need to go trough the whole dictionary again and instead just find it directly in the first positions.
How can I accomplish that with using rotate? Or do I need to do it with erase and insert because rotate doesnt work with pairs of vectors?

Answer 1

Consider making use of algorithms in the STL library. To use them, you have to get familiar with iterators. Then you can use something like std::rotate and it does not really matter what is in your vector.
For example your code can be refactored in the following way:
for (auto const& word : Text) {
auto it = std::find(Duden.begin(), Duden.end(), [&word](auto const& entry) {
return entry.first == word;
});
if(it == Duden.end()) {
continue;
}
generate_translation(uebersetzung, *it);
std::rotate(Duden.begin(), it, it+1);
}
The function generate_translation(std::vector<string>&, std::pair<string, string> const&) should be an own function to make the code more readable.
Something like
void generate_translation(std::vector<string>& uebersetzung,
std::pair<string, string> const& entry)
{
uebersetzung.push_back(entry.first);
if(entry.first.length() < 4){
uebersetzung.push_back(" ");
}
if(entry.first.length() < 8){
uebersetzung.push_back("\t");
} // These are only so it looks cleaner at the end
uebersetzung.push_back("\t\t\t\t: ");
uebersetzung.push_back(entry.second);
uebersetzung.push_back("\n");
}