class State$($object$)$:

def $\_\_$init$\_\_($self$,$ preceding$\_$action$)$:

$"""$

Initialize the State object.

$"""$

# each state MUST store the action that created it

# if you want to be able to actually see your solutions

self.action $=$ preceding$\_$action

pass

def $\_\_$str$\_\_($self$)$:

$"""$ A string representation of the State $"""$

return $""$

def $\_\_$eq$\_\_($self$,$ other$)$:

$"""$ Allows states to be compared"""

return False

class Problem$($object$)$:

$"""$The Problem class defines aspects of the problem.

One of the important definitions is the transition model for states.

To interact with search classes, the transition model is defined by:

is$\_$goal$($s$)$: returns true if the state is a goal state.

actions$($s$)$: returns a list of all legal actions in state s

result$($s$,$a$)$: returns a new state, the result of doing action a in state s

$"""$

def $\_\_$init$\_\_($self$,$ goal$)$:

$"""$ The problem is defined by a target value. We want to measure that many

liters of water.

:param goal: the number of liters of water we want to measure

$"""$

self.goal $=$ goal

# INSERT WHATEVER ELSE YOU NEED HERE

def create$\_$initial$\_$state$($self$)$:

$"""$ returns an initial state

$"""$

return None

def is$\_$goal$($self$,$ a$\_$state:State$)$:

$"""$Determine whether a$\_$state is a goal state"""

return False

def actions$($self$,$ a$\_$state:State$)$:

$"""$ Returns all the actions that are legal in the given state.

$"""$

return $[]$

def result$($self$,$ a$\_$state:State, an$\_$action$)$:

$"""$Implements the transition function.

Given a state and an action, return the resulting state.

$"""$

return None