HashSet c++ clarification

Question

I'm lost on this topic I have been studying. In my class we are implementing our own hash set class. Thus we have an underlying data structure , like a vector or array , and use a hash function to quickly determine whether an element is in the set it not . That is the part I do not follow. How would a hash function be used for this determination ?

The hash function tells you what bucket the element would be found in. — John Dibling, Oct 22 '14 at 20:15

score 0 · Accepted Answer · answered Oct 22 '14 at 20:10

imagine you have an underlying array of size 100, and you can only insert values from 0 to 99.

something like this:

class UselessHashMap
{
public:
  void insert(int value){
    _arr[hash(i)] = i;
  }
private:
  int hash(int i) { return i };
  std::array<int,100> _arr;
}

now, imagine you want to store more than 100 elements, and you can't have an array that has an infinite (std::numeric_limits::max() )size. In this case, your hash function will have to return you a value between 0-99, and of course your UselessHashMap class will need to take care of collisions as well, because that function could return the same value for different inputs.

HashSet c++ clarification

1 Answers1