Compare element in a vector with elements in an array

Question

I have two data structures with data in them.

• One is a vector std::vector<int> presentStudents And other is a
• char array char cAllowedStudents[256];

Now I have to compare these two such that checking every element in vector against the array such that all elements in the vector should be present in the array or else I will return false if there is an element in the vector that's not part of the array.

I want to know the most efficient and simple solution for doing this. I can convert my int vector into a char array and then compare one by one but that would be lengthy operation. Is there some better way of achieving this?

Answer 1

I would suggest you use a hash map (std::unordered_map). Store all the elements of the char array in the hash map.

Then simply sequentially check each element in your vector whether it is present in the map or not in O(1).

Total time complexity O(N), extra space complexity O(N).

Note that you will have to enable C++11 in your compiler.