Question

For instance. I have some structure:

s_Some{   std::string lable;   s_some_junk some_junk; }; 

And a vector:

std::vector<s_Some> mSome; 

And then I fill this vector with a lot of s_Somes.

I need to find an iterator for a single s_Some in this vector, which has a specific lable. So far I just iterate through all of this junk and match every lable with the one wanted. This looks a little bit stupid to me. Is there a better way to do so?

Answer 1

Option 1) If you are compelled to use the std::vector, but once the vector is filled it stays unchanged, then you could sort the vector and use the binary search. The only cost would be the sorting then and there will be no additional overhead. Searching time is logarithmic O(logN).

Option 2) If you have the freedom and can choose different data structure, then consider using the map (also logarithmic) or unordered_map ( expected O(1), worst O(n) ).

I have just noticed that you said you wanted to match every label with the one being looked for. So I conclude you can have duplicate labels. Then for point 2 use corresponding multi_map containers, while for point 1 things get a bit messier.