pseudo.py

Repeat: 
1- If frontier is empty:
	-Stop. There is no solution to the problem

2- Remove a node from the frontier. This is the node that will be considered

3- If the node contains the goal state:
	-Return the solution. Stop.

Else:
	Expand the node (find all the new nodes that could be reached from this node), 
	 and add resulting nodes to the frontier.

	Add the current node to the explored set.