Deutsch–Jozsa algorithm

The Deustch-Jozsa algorithm checks whether a function is constant of balanced. For example if we have a function that only gives as output either a 1 or a 0, then it is balanced if for exactly half the time it gives a 1, and for the other half of the time, a 0. It is constant if it returns only 1 all the time, or 0 all the time.