Hopfield network is the one other example of supervised learning.

Hopfield networks are motivated by particles in a magnetic field:-The idea for the Hopfield networks started from the behavior of particles in a magnetic field: Every particle "communicates"(through magnetic forces) with almost every particle (completely linked) with each particle trying to reach an energetically favorable state (i.e. at the least the energy function). As for the neurons this state is known as activation. Thus, all of the particles or neurons rotate and there by encourage one another to continue this rotation. As a way of speaking, our neural network is a cloud of particles Influenced by the reality that the particles automatically detect the minima of the energy function; Hopfield needed the idea to use the ôspin" of the particles to process information.